testsuite: g++.dg: torture: fix PR111520 filename

gcc/testsuite/ChangeLog:
	PR tree-optimization/111520

	* g++.dg/torture/harden-comp-pr111520.cc: Move to...
	* g++.dg/torture/harden-comp-pr111520.C: ...here.

diff --git a/gcc/testsuite/g++.dg/torture/harden-comp-pr111520.cc b/gcc/testsuite/g++.dg/torture/harden-comp-pr111520.C
similarity index 100%
rename from gcc/testsuite/g++.dg/torture/harden-comp-pr111520.cc
rename to gcc/testsuite/g++.dg/torture/harden-comp-pr111520.C