[llvm][docs] Remove LLDB DWARF64 release note

As a precaution until the issues reported (by me)
in llvm/llvm-project#135208
are investigated.

Author: DavidSpickett

llvm/docs/ReleaseNotes.md

@@ -304,7 +304,6 @@ Changes to LLDB
     stop reason = SIGSEGV: sent by tkill system call (sender pid=649752, uid=2667987)
   ```
 * ELF Cores can now have their siginfo structures inspected using `thread siginfo`.
-* LLDB now supports the `DWARF64` debugging information format.
 
 ### Changes to lldb-dap