[llvm] [CI] Tweak wording for builds with passing tests and build errors (PR #171436)

[David Spickett via llvm-commits]

DavidSpickett wrote:

I don't mind what it says as long as "all tests passed" is not literally in the text. It makes sense if you look more closely and think about it, but at a glance it's misleading. For example this one I saw today:

# :window: Windows x64 Test Results

* 2993 tests passed
* 30 tests skipped

All tests passed but another part of the build **failed**. Click on a failure below to see the details.

https://github.com/llvm/llvm-project/pull/171436