Use runStartupCommand instead of runMagicCommand

[DonJayamanne]

For #8485

[rchiodo]

Shouldn't we remove it from the package.json? I thought VS code did that with deprecated stuff eventually?

[DonJayamanne]

It never existed in the package.json, hence the PR, it hasn't been there for a long time.

[codecov-commenter]

Codecov Report

Merging #8486 (b5bc2ce) into main (74ca817) will increase coverage by 0%.
The diff coverage is 100%.

@@          Coverage Diff          @@
##            main   #8486   +/-   ##
=====================================
  Coverage     71%     71%           
=====================================
  Files        377     377           
  Lines      23913   23912    -1     
  Branches    3679    3677    -2     
=====================================
+ Hits       17200   17201    +1     
+ Misses      5253    5214   -39     
- Partials    1460    1497   +37     

Impacted Files	Coverage Δ
src/client/common/configSettings.ts	86% <ø> (-1%)	⬇️
src/client/common/types.ts	100% <ø> (ø)
src/client/datascience/jupyter/kernels/kernel.ts	76% <100%> (ø)
...ence/notebook/intellisense/intellisenseProvider.ts	83% <100%> (ø)
...lient/datascience/jupyter/kernels/cellExecution.ts	73% <0%> (-1%)	⬇️
src/client/debugger/jupyter/kernelDebugAdapter.ts	77% <0%> (-1%)	⬇️
src/client/api/pythonApi.ts	64% <0%> (ø)
src/client/common/configuration/service.ts	82% <0%> (ø)
src/client/datascience/jupyter/jupyterUtils.ts	65% <0%> (ø)
src/client/datascience/jupyter/jupyterSession.ts	72% <0%> (ø)
... and 10 more