Simplified YAML files for Github Actions workflows

Updated actions where needed

.github/workflows/linux_build_tests.yaml

@@ -23,23 +23,19 @@ on:
 
 jobs:
   build:
-
     runs-on: ubuntu-latest
     strategy:
-      max-parallel: 4
       matrix:
         package: [lz4, mpich, tut, py-setuptools, openjpeg, r-rcpp]
     steps:
     - uses: actions/checkout@v2
-    - name: Cache ccache's store
-      uses: actions/cache@v1
+    - uses: actions/cache@v2
       with:
         path: ~/.ccache
         key: ccache-build-${{ matrix.package }}
         restore-keys: |
           ccache-build-${{ matrix.package }}
-    - name: Setup Python
-      uses: actions/setup-python@v1
+    - uses: actions/setup-python@v2
       with:
         python-version: 3.8
     - name: Install System Packages