Updated email address in `CREDITS.txt`.

git-svn-id: https://llvm.org/svn/llvm-project/libcxx/trunk@297065 91177308-0d34-0410-b5e6-96231b3b80d8

CREDITS.TXT

@@ -81,7 +81,7 @@ E: andrew.c.morrow@gmail.com
 D: Minor patches and Linux fixes.
 
 N: Michael Park
-E: mpark@apache.org
+E: mcypark@gmail.com
 D: Implementation of <variant>.
 
 N: Arvid Picciani