ci: errno: check the workflow when changed

Make sure workflow is run when it is updated.

Signed-off-by: Gerard Marull-Paretas <[email protected]>

.github/workflows/errno.yml

@@ -2,6 +2,7 @@ name: Error numbers
 on:
   pull_request:
     paths:
+      - '.github/workflows/errno.yml'
       - 'lib/libc/minimal/include/errno.h'
       - 'scripts/ci/errno.py'