Fix link to good first issues

Author: Kobzol

src/tools/rust-analyzer/docs/book/src/contributing/README.md

@@ -30,7 +30,7 @@ Discussion happens in this Zulip stream:
 
 # Issue Labels
 
-* [good-first-issue](https://github.com/rust-lang/rust-analyzer/labels/good%20first%20issue)
+* [good-first-issue](https://github.com/rust-lang/rust-analyzer/issues?q=is%3Aissue%20state%3Aopen%20label%3A%22good%20first%20issue%22)
   are good issues to get into the project.
 * [E-has-instructions](https://github.com/rust-lang/rust-analyzer/issues?q=is%3Aopen+is%3Aissue+label%3AE-has-instructions)
   issues have links to the code in question and tests.