Don't use magic value for GOPLS_PARALLEL in Github CI

[taoeffect]

Problem

For optimizing make lint, in #123 the GOPLS_PARALLEL was set to 4 for Github's CI. This is a guess as to what it should be.

Solution

Set it to max(N - 1, 1) where N is the number of CPU cores on the machine.

This can be done by removing the manual GOPLS_PARALLEL value that was added to .github/workflows/pull-compliance.yml, and taking advantage of the code that was added in #130 to tools/lint-go-gopls.sh. Simply add an additional check for the Github CI environment, and if either that or Devin's environment is found, use max(N-1, 1).