fix: upgrade go version

Because some error messages has changed between 1.22 and 1.23 and the
one asserted in the txtar files are from 1.23

Author: tbruyelle

.github/workflows/go.yml

@@ -16,7 +16,7 @@ jobs:
     - name: Set up Go
       uses: actions/setup-go@v4
       with:
-        go-version: 1.21
+        go-version-file: go.mod
 
     - name: Build
       run: go build -v ./...

go.mod

@@ -1,6 +1,6 @@
 module github.com/gnolang/gnopls
 
-go 1.22.2
+go 1.23
 
 require (
 	github.com/dave/jennifer v1.7.0