Update docs to fit current compiler/doc state

Author: SLTozer

clang/docs/CommandGuide/clang.rst

@@ -445,7 +445,7 @@ Code Generation Options
 
     :option:`-Og` Similar to :option:`-O1`, but with slightly reduced
     optimization and better variable visibility. The same optimizations are run
-    as at :option:`-O1`, but the :option:`-fextend-variable-liveness` flag is
+    as at :option:`-O1`, but the ``-fextend-variable-liveness`` flag is
     also set, which tries to prevent optimizations from reducing the liveness of
     user variables, improving their availability when debugging.
 

clang/docs/ReleaseNotes.rst

@@ -221,9 +221,9 @@ Modified Compiler Flags
 
 - The ``-mexecute-only`` and ``-mpure-code`` flags are now accepted for AArch64 targets. (#GH125688)
 
-- The ``-Og`` optimization flag now sets ``-fextend-variable-liveness``, a new
-  compiler flag which trades a small amount of optimization in exchange for
-  improved variable visibility.
+- The ``-Og`` optimization flag now sets ``-fextend-variable-liveness``,
+  reducing performance slightly while reducing the number of optimized-out
+  variables.
 
 Removed Compiler Flags
 -------------------------