static-checks: Restrict static checks to go 1.15 and 1.16

Seems that we get different results when running it with go 1.13.
Instead of figuring out why it doesn't work as expected with an EOL
version of go, let's just not run the tests on go versions that are
already dead.

https://endoflife.date/go

Depends-on: github.com/kata-containers/tests#3808
Signed-off-by: Fabiano Fidêncio <fidencio@redhat.com>

.github/workflows/static-checks.yaml

@@ -4,7 +4,7 @@ jobs:
   test:
     strategy:
       matrix:
-        go-version: [1.13.x, 1.14.x, 1.15.x]
+        go-version: [1.15.x, 1.16.x]
         os: [ubuntu-20.04]
     runs-on: ${{ matrix.os }}
     env: