Fix file extension of alignment-assumption-ignorelist.cppp test

During the renaming of blacklist to ignorelist this test got renamed
incorrectly.

Differential revision: https://reviews.llvm.org/D114710

GitOrigin-RevId: 455a2b824d7734939e54cfb3f47c054517f75be8
diff --git a/test/ubsan/TestCases/Pointer/alignment-assumption-ignorelist.cppp b/test/ubsan/TestCases/Pointer/alignment-assumption-ignorelist.cpp
similarity index 100%
rename from test/ubsan/TestCases/Pointer/alignment-assumption-ignorelist.cppp
rename to test/ubsan/TestCases/Pointer/alignment-assumption-ignorelist.cpp