Use fail-fast: false in mypy.yml (python#119297)

See docs about this setting: https://docs.github.com/en/actions/using-workflows/workflow-syntax-for-github-actions#jobsjob_idstrategyfail-fast

Author: sobolevn

.github/workflows/mypy.yml

@@ -34,6 +34,7 @@ concurrency:
 jobs:
   mypy:
     strategy:
+      fail-fast: false
       matrix:
         target: [
           "Lib/_pyrepl",