[LLD] [COFF] Fix test to properly test all aspects of c3b1d73. NFC.

Previously, the test could pass with one part of c3b1d73 removed.

Author: mstorsjo

lld/test/COFF/associative-comdat-mingw-i386.s

@@ -30,7 +30,7 @@ _main:
         .scl            2;
         .type           32;
         .endef
-        .section        .text$foo,"xr",discard,foo
+        .section        .text$foo,"xr",discard,_foo
         .globl          _foo
         .p2align        4
 _foo: