[llvm] [Windows][test] Fix "LLVM" test failures when LLVM_WINDOWS_PREFER_FORWARD_SLASH is ON (PR #184556)

[James Henderson via llvm-commits]

================
@@ -23,13 +23,13 @@
 
 
 
-# HTML-TOP: coverage\index.html
+# HTML-TOP: coverage{{[/\\]}}index.html
----------------
jh7370 wrote:

Looking at the review for this test (see https://reviews.llvm.org/D151283#4605381), it looks like it might have been intentional to have `\` in the paths, since those are the traditional Windows paths. @gulfemsavrun / @phosek / @yhgu2000 any input?

https://github.com/llvm/llvm-project/pull/184556