[3.12] gh-105063: Disable test_peg_generator.TestCParser bco. ref leaks (GH-106024) (#106450)

Since gh-104798 (Use setuptools in peg-generator and reenable
tests), the TestCParser test case has been producing ref leaks.
(cherry picked from commit 41ad4dfc04c201728ce9fa12b1a96922dd15a368)

Co-authored-by: Erlend E. Aasland <erlend.aasland@protonmail.com>