(build) Fix yaml syntax

Remove the usage of ' which are not required when passing an array of
versions, only when using a single version.

Author: gep13

.github/workflows/build.yml

@@ -30,8 +30,8 @@ jobs:
         uses: actions/setup-dotnet@v3
         with:
           dotnet-version: |
-            '3.1.x'
-            '5.0.x'
+            3.1.x
+            5.0.x
 
       - name: Cache Tools
         uses: actions/cache@v2