github : minify link [no ci] (revert)

this doesn't work as expected

.github/pull_request_template.md

@@ -1 +1 @@
-*Make sure to read the [contributing guidelines](CONTRIBUTING.md) before submitting a PR*
+*Make sure to read the [contributing guidelines](https://github.com/ggerganov/llama.cpp/blob/master/CONTRIBUTING.md) before submitting a PR*