[clang-tidy] Fix documentation (NFC)

The documentation files were reorganized into subdirectories, but a new
check was added concurrently and wasn't rebased correctly before
submitting.  Sort the new clang-tidy checks by check name and fix the
indentation of bugprone-unchecked-optional-access.

clang-tools-extra/docs/ReleaseNotes.rst

@@ -123,8 +123,12 @@ New checks
 - New :doc:`bugprone-unchecked-optional-access
   <clang-tidy/checks/bugprone/unchecked-optional-access>` check.
 
-   Warns when the code is unwrapping a `std::optional<T>`, `absl::optional<T>`,
-   or `base::Optional<T>` object without assuring that it contains a value.
+  Warns when the code is unwrapping a `std::optional<T>`, `absl::optional<T>`,
+  or `base::Optional<T>` object without assuring that it contains a value.
+
+- New :doc:`misc-confusable-identifiers <clang-tidy/checks/misc/confusable-identifiers>` check.
+
+  Detects confusable Unicode identifiers.
 
 - New :doc:`modernize-macro-to-enum
   <clang-tidy/checks/modernize/macro-to-enum>` check.
@@ -139,10 +143,6 @@ New checks
   Future libc++ will remove the extension (`D120996
   <https://reviews.llvm.org/D120996>`).
 
-- New :doc:`misc-confusable-identifiers <clang-tidy/checks/misc-confusable-identifiers` check.
-
-  Detects confusable Unicode identifiers.
-
 New check aliases
 ^^^^^^^^^^^^^^^^^