gdb: update to 16.2
See news file for changes:
https://sourceware.org/git/gitweb.cgi?p=binutils-gdb.git;a=blob_plain;f=gdb/NEWS;hb=gdb-16.2-release
It fixes compilation with GCC15.
Link: https://github.com/openwrt/openwrt/pull/18519
Signed-off-by: Robert Marko <[email protected]>