Use (go install) instead of (go get)

This use of (go get) was deprecated back in Go 1.18.

Also don't use our build tags for building unrelated tools.

Signed-off-by: Miloslav Trmač <mitr@redhat.com>

Makefile

@@ -66,7 +66,7 @@ tools: .install.gitvalidation .install.golangci-lint
 
 .install.gitvalidation:
 	if [ ! -x "$(GOBIN)/git-validation" ]; then \
-		GO111MODULE="off" go get $(BUILDFLAGS) github.com/vbatts/git-validation; \
+		go install github.com/vbatts/git-validation@latest; \
 	fi
 
 .install.golangci-lint: