[clang][test] zero-init-empty-virtual.cpp: remove redundant alignment check

Fixes a `clang-armv8-quick` buildbot failure. Where the alignment
was `4` instead of `8`:
```
// CHECK: @{{.*}} = {{.*}}global %struct.Holder2 zeroinitializer, align 8
          ^
<stdin>:66:178: note: scanning from here
@g_holder1 = global %struct.Holder1 { %struct.polymorphic_base { ptr getelementptr inbounds inrange(-8, 12) ({ [5 x ptr] }, ptr @_ZTV16polymorphic_base, i32 0, i32 0, i32 2) } }, align 4
                                                                                                                                                                                 ^
<stdin>:68:8: note: possible intended match here
@g_holder2 = global %struct.Holder2 zeroinitializer, align 4
       ^
```

This test isn't about checking alignment, so remove that from the
FileCheck entry.

Author: Michael137

clang/test/CodeGenCXX/zero-init-empty-virtual.cpp

@@ -26,7 +26,7 @@ struct Holder2 {
   derived_virtual a{};
 } g_holder2;
 
-// CHECK: @{{.*}} = {{.*}}global %struct.Holder2 zeroinitializer, align 8
+// CHECK: @{{.*}} = {{.*}}global %struct.Holder2 zeroinitializer
 
 struct Holder3 {
   derived a{};