change contributing steps from installing pnpm@7 to pnpm@8

[rhino88]

Unable to run contributing steps due to:

 ERR_PNPM_UNSUPPORTED_ENGINE  Unsupported environment (bad pnpm and/or Node.js version)

Your pnpm version is incompatible with "/Users/ryan/Code/graphql-yoga".

Expected version: >=8.6.1
Got: 7.33.6

This is happening because the package's manifest has an engines.pnpm field specified.
To fix this issue, install the required pnpm version globally.

This will bump the pnpm version to 8 in the steps for creating a failing test case.

[changeset-bot]

⚠️ No Changeset found

Latest commit: e50e140

Merging this PR will not cause a version bump for any packages. If these changes should not result in a new version, you're good to go. If these changes should result in a version bump, you need to add a changeset.

This PR includes no changesets

When changesets are added to this PR, you'll see the packages that this PR includes changesets for and the associated semver types

Click here to learn what changesets are, and how to add one.

Click here if you're a maintainer who wants to add a changeset to this PR

[EmrysMyrddin]

Good catch thank you !

[github-actions]

✅ Benchmark Results

     ✓ no_errors{mode:graphql}
     ✓ expected_result{mode:graphql}
     ✓ no_errors{mode:graphql-jit}
     ✓ expected_result{mode:graphql-jit}
     ✓ no_errors{mode:graphql-response-cache}
     ✓ expected_result{mode:graphql-response-cache}
     ✓ no_errors{mode:graphql-no-parse-validate-cache}
     ✓ expected_result{mode:graphql-no-parse-validate-cache}

     checks.......................................: 100.00% ✓ 386592      ✗ 0     
     data_received................................: 1.6 GB  13 MB/s
     data_sent....................................: 78 MB   650 kB/s
     http_req_blocked.............................: avg=1.56µs   min=1µs      med=1.38µs   max=305.06µs p(90)=2.05µs   p(95)=2.25µs  
     http_req_connecting..........................: avg=2ns      min=0s       med=0s       max=141.17µs p(90)=0s       p(95)=0s      
     http_req_duration............................: avg=394.24µs min=221.75µs med=343.49µs max=18.05ms  p(90)=564.18µs p(95)=595.11µs
       { expected_response:true }.................: avg=394.24µs min=221.75µs med=343.49µs max=18.05ms  p(90)=564.18µs p(95)=595.11µs
     ✓ { mode:graphql-jit }.......................: avg=296.33µs min=221.75µs med=274.7µs  max=18.05ms  p(90)=302.98µs p(95)=314.8µs 
     ✓ { mode:graphql-no-parse-validate-cache }...: avg=599.26µs min=481.64µs med=564.21µs max=10.09ms  p(90)=636.91µs p(95)=689.02µs
     ✓ { mode:graphql-response-cache }............: avg=356.75µs min=280.11µs med=337.28µs max=6.62ms   p(90)=367.76µs p(95)=379.17µs
     ✓ { mode:graphql }...........................: avg=397.19µs min=298.84µs med=363.7µs  max=13.13ms  p(90)=412.21µs p(95)=444.95µs
     http_req_failed..............................: 0.00%   ✓ 0           ✗ 193296
     http_req_receiving...........................: avg=33.82µs  min=17.32µs  med=33.79µs  max=913.86µs p(90)=39.4µs   p(95)=41.72µs 
     http_req_sending.............................: avg=8.83µs   min=6.04µs   med=7.87µs   max=605.66µs p(90)=11.49µs  p(95)=12.67µs 
     http_req_tls_handshaking.....................: avg=0s       min=0s       med=0s       max=0s       p(90)=0s       p(95)=0s      
     http_req_waiting.............................: avg=351.58µs min=191.95µs med=301.45µs max=17.93ms  p(90)=520.85µs p(95)=550.82µs
     http_reqs....................................: 193296  1610.779943/s
     iteration_duration...........................: avg=615.87µs min=401.95µs med=560.35µs max=18.55ms  p(90)=786.67µs p(95)=822.69µs
     iterations...................................: 193296  1610.779943/s
     vus..........................................: 1       min=1         max=1   
     vus_max......................................: 2       min=2         max=2