gdb: fix amd_dbgapi_target_breakpoint::re_set's signature

Following

        commit 6cce0251
        Date:   Fri Mar 3 19:03:15 2023 +0000

            gdb: only insert thread-specific breakpoints in the relevant inferior

... when building amd-dbgapi-target.c:

      CXX    amd-dbgapi-target.o
    /home/smarchi/src/binutils-gdb/gdb/amd-dbgapi-target.c:486:8: error: ‘void amd_dbgapi_target_breakpoint::re_set()’ marked ‘override’, but does not override
      486 |   void re_set () override;
          |        ^~~~~~

Update the signature to match the base.

Change-Id: Ie8bd71a63284917180f3e67eead58bea74bb0692