docs: update Angular's commit convention link (vuejs#7666)

sis0k0 · hefeng · commit ba7bdd14237b · 2019-01-25T17:43:41.000+08:00
diff --git a/.github/COMMIT_CONVENTION.md b/.github/COMMIT_CONVENTION.md
@@ -1,6 +1,6 @@
 ## Git Commit Message Convention
 
-> This is adapted from [Angular's commit convention](https://github.com/conventional-changelog/conventional-changelog/blob/master/packages/conventional-changelog-angular/convention.md).
+> This is adapted from [Angular's commit convention](https://github.com/conventional-changelog/conventional-changelog/tree/master/packages/conventional-changelog-angular).
 
 #### TL;DR:
 
