Bump scala version to 2.12.13 in workflows

Problem/Solution

We've updated the supported scala version in the sbt files
lets follow up with the CI workflows. Util was already done
in the first update.

Differential Revision: https://phabricator.twitter.biz/D635494

.github/workflows/continuous-integration.yml

@@ -19,7 +19,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        scala: [2.12.8, 2.13.1]
+        scala: [2.12.13, 2.13.1]
         java: ['1.8', '1.11']
     runs-on: ubuntu-latest
     steps: