ci: kin-openapi3 only supports Go greater than 1.19

Author: aereal

.github/workflows/ci.yml

@@ -19,7 +19,6 @@ jobs:
         go_version:
           - 1.21.x
           - 1.20.x
-          - 1.19.x
         os:
           - ubuntu-latest
     runs-on: ${{ matrix.os }}