[docs] Clean up introduction

Author: patricklodder

CONTRIBUTING.md

@@ -1,8 +1,8 @@
 # Contributing to Dogecoin Core
 
-Dogecoin Core is an open source project, and we would welcome contributions which provably
-improve the state of the software. For those wanting to discuss changes, or look for work
-that needs doing, please see:
+Dogecoin Core is open source software, and we would welcome contributions
+which improves the state of the software. For those wanting to discuss changes,
+or look for work that needs doing, please see:
 
 * [Help requests](https://github.com/dogecoin/dogecoin/labels/help%20wanted)
 * [Projects](https://github.com/dogecoin/dogecoin/projects)