gh-102809: Remove gdbinit mention in Misc/README (#103269)

Author: hrnciar

Misc/README

@@ -8,7 +8,6 @@ Files found here
 ----------------
 
 ACKS                    Acknowledgements
-gdbinit                 Handy stuff to put in your .gdbinit file, if you use gdb
 HISTORY                 News from previous releases -- oldest last
 indent.pro              GNU indent profile approximating my C style
 NEWS                    News for this release (for some meaning of "this")