Docs: note Rosetta 2 requirement for Apple Silicon

Replace the Apple Silicon supported-platforms footnote with guidance on
when Rosetta 2 is needed: building your code during analysis requires
Rosetta 2, while analyzing an interpreted language or using build mode
none runs natively.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>

Author: redsun82

docs/codeql/reusables/supported-platforms.rst

@@ -20,4 +20,4 @@
 
     .. [1] Support for Linux on arm64 is currently in beta.
 
-    .. [2] Support for Apple Silicon is currently in beta.
+    .. [2] On Apple Silicon, building your code during analysis requires Rosetta 2; analyzing an interpreted language or using build mode ``none`` runs natively.