Fix links to commit lists in release-notes.md (#555)

Author: ExplodingCabbage

release-notes.md

@@ -4,7 +4,7 @@
 
 This is a release containing many, *many* breaking changes. The objective of this release was to carry out a mass fix, in one go, of all the open bugs and design problems that required breaking changes to fix. A substantial, but exhaustive, changelog is below.
 
-[Commits](https://github.com/kpdecker/jsdiff/compare/master...v6.0.0-staging)
+[Commits](https://github.com/kpdecker/jsdiff/compare/v5.2.0...v6.0.0)
 
 - [#497](https://github.com/kpdecker/jsdiff/pull/497) **`diffWords` behavior has been radically changed.** Previously, even with `ignoreWhitespace: true`, runs of whitespace were tokens, which led to unhelpful and unintuitive diffing behavior in typical texts. Specifically, even when two texts contained overlapping passages, `diffWords` would sometimes choose to delete all the words from the old text and insert them anew in their new positions in order to avoid having to delete or insert whitespace tokens. Whitespace sequences are no longer tokens as of this release, which affects both the generated diffs and the `count`s.
 
@@ -40,7 +40,7 @@ This is a release containing many, *many* breaking changes. The objective of thi
 
 ## v5.2.0
 
-[Commits](https://github.com/kpdecker/jsdiff/compare/v5.1.0...master)
+[Commits](https://github.com/kpdecker/jsdiff/compare/v5.1.0...v5.2.0)
 
 - [#411](https://github.com/kpdecker/jsdiff/pull/411) Big performance improvement. Previously an O(n) array-copying operation inside the innermost loop of jsdiff's base diffing code increased the overall worst-case time complexity of computing a diff from O(n²) to O(n³). This is now fixed, bringing the worst-case time complexity down to what it theoretically should be for a Myers diff implementation.
 - [#448](https://github.com/kpdecker/jsdiff/pull/411) Performance improvement. Diagonals whose furthest-reaching D-path would go off the edge of the edit graph are now skipped, rather than being pointlessly considered as called for by the original Myers diff algorithm. This dramatically speeds up computing diffs where the new text just appends or truncates content at the end of the old text.