remove some ancient Scala versions

Author: SethTisue

.github/workflows/validate.yml

@@ -14,26 +14,8 @@ jobs:
       fail-fast: false
       matrix:
         scala:
-          - 2.12.5
-          - 2.12.6
-          - 2.12.7
-          - 2.12.8
-          - 2.12.9
-          - 2.12.10
-          - 2.12.11
-          - 2.12.12
-          - 2.12.13
-          - 2.12.14
-          - 2.12.15
-          - 2.12.16
-          - 2.12.17
           - 2.12.18
           - 2.12.19
-          - 2.13.0
-          - 2.13.1
-          - 2.13.2
-          - 2.13.3
-          - 2.13.4
           - 2.13.5
           - 2.13.6
           - 2.13.7