Fix issues identified by Julia Package Butler

Author: Julia Package Butler

.github/workflows/jlpkgbutler-ci-master-workflow.yml

@@ -10,7 +10,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        julia-version: ['1.3', '1.4', '1.5']
+        julia-version: ['1.3', '1.4', '1.5', '1.6']
         julia-arch: [x64, x86]
         os: [ubuntu-latest, windows-latest, macOS-latest]
         exclude:

.github/workflows/jlpkgbutler-ci-pr-workflow.yml

@@ -9,7 +9,7 @@ jobs:
     runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        julia-version: ['1.3', '1.4', '1.5']
+        julia-version: ['1.3', '1.4', '1.5', '1.6']
         julia-arch: [x64, x86]
         os: [ubuntu-latest, windows-latest, macOS-latest]
         exclude: