[llvm][docs] Improve usage note on stacked PRs (#138949)

Author: paschalis-mpeis

llvm/docs/GitHub.rst

@@ -292,9 +292,9 @@ Your options are as follows:
    subsequent PRs in a stack. Instead, it will show a combined diff that
    includes all commits from earlier PRs.
 
-   As described in the first option above, in such cases it is the PR author’s
-   responsibility to clearly indicate which commits are relevant to the
-   current PR. For example: “The first N commits are from the base PR.”
+   As described above, it is the PR author’s responsibility to clearly indicate
+   which commits are relevant to the current PR.
+   For example: “The first N commits are from the base PR.”
 
    You can avoid this issue by using user branches directly in the
    ``llvm/llvm-project`` repository.