[797] "Good First Issue" Link is Broken in CONTRIBUTING.md (#840)

- Fixed the "Good First Issue" Link in "Your First Code Contribution" section of /CONTRIBUTING.md
Signed-off-by: Adrian Sutton <adrian.sutton@consensys.net>

CONTRIBUTING.md

@@ -217,7 +217,7 @@ We have a set of [coding conventions](CODING-CONVENTIONS.md) to which we try to
 [search-label-enhancement]: https://github.com/search?q=is%3Aopen+is%3Aissue+repo%3APegasysEng%2FPantheon+label%3Aenhancement
 [search-label-bug]: https://github.com/search?q=is%3Aopen+is%3Aissue+repo%3APegasysEng%2FPantheon+label%3Abug
 [search-label-help-wanted]: https://github.com/search?q=is%3Aopen+is%3Aissue+repo%3APegasysEng%2FPantheon+label%3Ahelp%20wanted
-[search-label-good-first-issue]: https://github.com/search?q=is%3Aopen+is%3Aissue+repo%3APegasysEng%2FPantheon+label%3Agood%20first%20issue
+[search-label-good-first-issue]: https://github.com/PegasysEng/pantheon/issues?q=is%3Aissue+is%3Aopen+label%3A%22good+first+issue%22
 [search-label-info-needed]: https://github.com/search?q=is%3Aopen+is%3Aissue+repo%3APegasysEng%2FPantheon+label%3Ainfo%20needed
 [search-label-needs-reproduction]: https://github.com/search?q=is%3Aopen+is%3Aissue+repo%3APegasysEng%2FPantheon+label%3Aneeds%20reproduction
 [search-label-blocked]: https://github.com/search?q=is%3Aopen+is%3Aissue+repo%3APegasysEng%2FPantheon+label%3Ablocked