codecov: increase project threshold to 2% (#46828)

We run tests for more python versions on `develop` than we do for PRs, so codecov
project status is nearly always failing. There is about a 1% difference in max coverage
between `develop` tests and PR tests, so we should increase the project threshold to 2%
to allow for this difference.

The purpose of the project test on PRs is just to make sure that nothing done on the PR
massively affects coverage of code not covered by the PR. This is valuable, but rare. It
only really affects PRs that deal with test or coverage configuration.

- [x] change project coverage threshold from .2% to 2%

Signed-off-by: Todd Gamblin <tgamblin@llnl.gov>

.codecov.yml

@@ -5,7 +5,7 @@ coverage:
   status:
     project:
       default:
-        threshold: 0.2%
+        threshold: 2.0%
 
 ignore:
   - lib/spack/spack/test/.*