bump LTS 1.3 -> 1.6

Author: Moelf

.github/workflows/UnitTest.yml

@@ -14,7 +14,7 @@ jobs:
     strategy:
       fail-fast: false
       matrix:
-        julia-version: ['1.3', '1', 'nightly']
+        julia-version: ['1.6', '1', 'nightly']
         os: [ubuntu-latest, windows-latest, macOS-latest]
 
     steps: