[llvm] [VFABI] Improve VFABI unit tests (PR #73907)

[Graham Hunter via llvm-commits]

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@@ -34,20 +35,22 @@ class VFABIParserTest : public ::testing::Test {
         << "The function must be present in the module\n";
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huntergr-arm wrote:

I don't think we need to add a function with the mangled name (above) anymore; just having a module and the scalar function type is enough.

https://github.com/llvm/llvm-project/pull/73907