tests: reduce timeout to 4m from 8m (#7681)

Makefile

@@ -308,4 +308,4 @@ $(BUILDDIR)/packages.txt:$(GO_TEST_FILES) $(BUILDDIR)
 split-test-packages:$(BUILDDIR)/packages.txt
 	split -d -n l/$(NUM_SPLIT) $< $<.
 test-group-%:split-test-packages
-	cat $(BUILDDIR)/packages.txt.$* | xargs go test -mod=readonly -timeout=8m -race -coverprofile=$(BUILDDIR)/$*.profile.out
+	cat $(BUILDDIR)/packages.txt.$* | xargs go test -mod=readonly -timeout=5m -race -coverprofile=$(BUILDDIR)/$*.profile.out