[3.10] GH-102711: Fix warnings found by clang (GH-102712) (#103076)

There are some warnings if build python via clang:

Parser/pegen.c:812:31: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
_PyPegen_clear_memo_statistics()
                              ^
                               void

Parser/pegen.c:820:29: warning: a function declaration without a prototype is deprecated in all versions of C [-Wstrict-prototypes]
_PyPegen_get_memo_statistics()
                            ^
                             void

Fix it to make clang happy.

(cherry picked from commit 7703def37e4fa7d25c3d23756de8f527daa4e165)

Signed-off-by: Chenxi Mao <chenxi.mao@suse.com>
Co-authored-by: Chenxi Mao <chenxi.mao@suse.com>