ci: install gofumpt and golangci-lint in same step to fix PATH

Previous attempts failed because go install puts binaries in GOPATH/bin
which may not be in PATH for subsequent steps. Combine into fewer steps.

.gitea/workflows/ci.yml

@@ -32,11 +32,10 @@ jobs:
             exit 1
           fi
 
-      - name: Install golangci-lint
-        run: go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest
-
       - name: Run lint
-        run: golangci-lint run ./...
+        run: |
+          go install github.com/golangci/golangci-lint/v2/cmd/golangci-lint@latest
+          golangci-lint run ./...
 
   test:
     name: Test