Remove GitSponsors badge

Author: AArnott

README.md

@@ -55,7 +55,7 @@ public void TestCngKey()
 
 ## Sponsorships
 
-[<img src="https://api.gitsponsors.com/api/badge/img?id=39364524" height="20">](https://api.gitsponsors.com/api/badge/link?p=gfTAaPbnYnow49AIjp8+x6zqItEv9S5jyYxbQltcORwVT6sruhrlqC8A/BAUipwCTnxBrMnnlPhVz2HXELTWe3KqMHrfiusNcB64Wnh4efdCTfCjt5lR/fofmSyjWbMoakjbDpQOHfWcwGy1lvsUbw==) [GitHub Sponsors](https://github.com/sponsors/AArnott)
+[GitHub Sponsors](https://github.com/sponsors/AArnott)
 [Zcash](zcash:u1vv2ws6xhs72faugmlrasyeq298l05rrj6wfw8hr3r29y3czev5qt4ugp7kylz6suu04363ze92dfg8ftxf3237js0x9p5r82fgy47xkjnw75tqaevhfh0rnua72hurt22v3w3f7h8yt6mxaa0wpeeh9jcm359ww3rl6fj5ylqqv54uuwrs8q4gys9r3cxdm3yslsh3rt6p7wznzhky7)
 
 [NuPkg]: https://www.nuget.org/packages/Xunit.SkippableFact