Tweak description copy.

Author: afinetooth

Diff for: action.yml

@@ -23,7 +23,7 @@ inputs:
     description: 'Job flag name, e.g. "Unit", "Functional", or "Integration". Will be shown in the Coveralls UI.'
     required: false
   build-number:
-    description: 'Override the build number autodetected from CI. This is useful if your CI tool assigns a different build number per parallel build.'
+    description: 'Override the build number autodetected from CI. This is useful if your CI tool assigns a different build number per each parallel build.'
     required: false
   parallel:
     description: 'Set to true if you are running parallel jobs, then use "parallel-finished: true" for the last action.'