Fix Go version in go.build.yaml

From the `actions/setup-go` documentation:

> Due to the peculiarities of YAML parsing, it is recommended to wrap the version in single quotation marks: […]
>
> The recommendation is based on the YAML parser's behavior, which interprets non-wrapped values as numbers and, in the case of version 1.20, trims it down to 1.2, which may not be very obvious.

.github/workflows/go.build.yaml

@@ -18,7 +18,7 @@ jobs:
       - name: Set up Go 1.20
         uses: actions/setup-go@v4
         with:
-          go-version: 1.20
+          go-version: '1.20'
         id: go
 
       - name: Check out code into the Go module directory