fixed github actions

Author: jornbr

.github/workflows/gotm.yml

@@ -4,12 +4,15 @@ jobs:
    gfortran:
       strategy:
          matrix:
-            version: [7, 8, 9, 10]
+            version: [9, 10]
             os: [ubuntu-latest]
             include:
                - version: 6
                  os: ubuntu-18.04
+               - version: 7
+                 os: ubuntu-20.04
                - version: 8
+                 os: ubuntu-20.04
                  cmake_args: -DFABM_USE_CONTIGUOUS=OFF
          fail-fast: false
       runs-on: ${{ matrix.os }}