Fix github issue query

[tevoinea]

Need to set is:issue even when querying for issues.

[codecov-commenter]

Codecov Report

Merging #2514 (0f70cdf) into main (58b3d6f) will increase coverage by 0.20%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##             main    #2514      +/-   ##
==========================================
+ Coverage   29.76%   29.96%   +0.20%     
==========================================
  Files         282      289       +7     
  Lines       33829    35421    +1592     
==========================================
+ Hits        10068    10615     +547     
- Misses      23761    24806    +1045     

Impacted Files	Coverage Δ
...piService/onefuzzlib/notifications/GithubIssues.cs	0.00% <0.00%> (ø)
src/agent/coverage/src/code.rs	14.41% <0.00%> (-5.24%)	⬇️
src/agent/onefuzz/src/fs.rs	55.55% <0.00%> (-4.37%)	⬇️
...c/agent/dynamic-library/src/bin/dynamic-library.rs	2.38% <0.00%> (-0.40%)	⬇️
src/agent/onefuzz-agent/src/worker.rs	62.00% <0.00%> (-0.38%)	⬇️
src/agent/onefuzz/src/process.rs	1.33% <0.00%> (-0.16%)	⬇️
src/agent/onefuzz/src/asan.rs	0.00% <0.00%> (ø)
src/agent/coverage/src/cache.rs	0.00% <0.00%> (ø)
src/agent/coverage/src/debuginfo.rs	0.00% <0.00%> (ø)
src/agent/onefuzz-agent/src/setup.rs	0.00% <0.00%> (ø)
... and 22 more

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.