[doc] Remove release notes from the main branch for changes that were backported to 15.x

clang/docs/ReleaseNotes.rst

@@ -91,13 +91,6 @@ Improvements to Clang's diagnostics
   language modes. It may be downgraded to a warning with
   ``-Wno-error=incompatible-function-pointer-types`` or disabled entirely with
   ``-Wno-implicit-function-pointer-types``.
-- When including a PCH from a GCC style directory with multiple alternative PCH
-  files, Clang now requires all defines set on the command line while generating
-  the PCH and when including it to match. This matches GCC's behaviour.
-  Previously Clang would tolerate defines to be set when creating the PCH but
-  missing when used, or vice versa. This makes sure that Clang picks the
-  correct one, where it previously would consider multiple ones as potentially
-  acceptable (and erroneously use whichever one is tried first).
 - Clang will now print more information about failed static assertions. In
   particular, simple static assertion expressions are evaluated to their
   compile-time value and printed out if the assertion fails.

lld/docs/ReleaseNotes.rst

@@ -39,11 +39,7 @@ COFF Improvements
 MinGW Improvements
 ------------------
 
-* The ``--exclude-symbols`` option is now supported.
-  (`D130118 <https://reviews.llvm.org/D130118>`_)
-
-* Support for an entirely new object file directive, ``-exclude-symbols:``,
-  has been implemented. (`D130120 <https://reviews.llvm.org/D130120>`_)
+* ...
 
 MachO Improvements
 ------------------