Ensure environment variables are always strings in launch.json

[karthiknadig]

For #9568

• Pull request represents a single change (i.e. not fixing disparate/unrelated things in a single PR)
• Title summarizes what is changing
• Has a news entry file (remember to thank yourself!)
• Appropriate comments and documentation strings in the code
• Has sufficient logging.
• Has telemetry for enhancements.
• Unit tests & system/integration tests are added/updated
• Test plan is updated as appropriate
• package-lock.json has been regenerated by running npm install (if dependencies have changed)
• The wiki is updated with any design decisions/details.

[sonarcloud]

Kudos, SonarCloud Quality Gate passed!

0 Bugs
0 Vulnerabilities (and 0 Security Hotspots to review)
0 Code Smells

No Coverage information
No Duplication information

[codecov-io]

Codecov Report

Merging #9728 into master will decrease coverage by 0.06%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master    #9728      +/-   ##
==========================================
- Coverage   60.71%   60.65%   -0.07%     
==========================================
  Files         552      552              
  Lines       29736    29778      +42     
  Branches     4495     4505      +10     
==========================================
+ Hits        18055    18061       +6     
- Misses      10670    10706      +36     
  Partials     1011     1011

Impacted Files	Coverage Δ
...ence/interactive-common/intellisense/conversion.ts	36.11% <0%> (-3.02%)	⬇️
src/client/activation/refCountedLanguageServer.ts	37.2% <0%> (-2.8%)	⬇️
...active-common/intellisense/intellisenseProvider.ts	35.54% <0%> (-2.24%)	⬇️
src/client/activation/jedi.ts	21.21% <0%> (-0.67%)	⬇️
...ience/interactive-common/interactiveWindowTypes.ts	100% <0%> (ø)	⬆️

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[ericsnowcurrently]

LGTM

I guess the only real way to test this is manually. It may be worth adding to the test plan (or maybe not since we don't test any other part of that schema).