Rollup merge of rust-lang#125395 - madsmtm:fix-doc-summary, r=lqd

Remove unnecessary `.md` from the documentation sidebar

Oversight from rust-lang#124772, caught in rust-lang#124772 (comment).

r? weihanglo

src/doc/rustc/src/SUMMARY.md

@@ -20,10 +20,10 @@
     - [\*-apple-darwin](platform-support/apple-darwin.md)
         - [i686-apple-darwin](platform-support/i686-apple-darwin.md)
         - [x86_64h-apple-darwin](platform-support/x86_64h-apple-darwin.md)
-        - [arm64e-apple-darwin.md](platform-support/arm64e-apple-darwin.md)
+        - [arm64e-apple-darwin](platform-support/arm64e-apple-darwin.md)
     - [\*-apple-ios](platform-support/apple-ios.md)
         - [\*-apple-ios-macabi](platform-support/apple-ios-macabi.md)
-        - [arm64e-apple-ios.md](platform-support/arm64e-apple-ios.md)
+        - [arm64e-apple-ios](platform-support/arm64e-apple-ios.md)
     - [\*-apple-tvos](platform-support/apple-tvos.md)
     - [\*-apple-watchos](platform-support/apple-watchos.md)
     - [\*-apple-visionos](platform-support/apple-visionos.md)