[MemLoc] Specify LocationSize in unit test

Followup to 393b9e9,
where I missed updating one MemoryLocation use inside a unit test.

llvm/unittests/Analysis/MemorySSATest.cpp

@@ -1277,7 +1277,7 @@ TEST_F(MemorySSATest, LifetimeMarkersAreClobbers) {
 
   MemoryAccess *LifetimeStartClobber =
       MSSA.getWalker()->getClobberingMemoryAccess(
-          LifetimeStartAccess, MemoryLocation(Foo));
+          LifetimeStartAccess, MemoryLocation(Foo, LocationSize::unknown()));
   EXPECT_EQ(LifetimeStartClobber, LifetimeStartAccess);
 }