Revert "[lldb][progress][NFC] Add unit test for progress reports (llvm#79533)"

This reverts commit 51e0d1b.
That commit breaks a unit test:

```
Failed Tests (1):
  lldb-unit :: Core/./LLDBCoreTests/4/8
```

Author: chelcassanova

lldb/unittests/Core/CMakeLists.txt

@@ -7,7 +7,6 @@ add_lldb_unittest(LLDBCoreTests
   FormatEntityTest.cpp
   MangledTest.cpp
   ModuleSpecTest.cpp
-  ProgressReportTest.cpp
   RichManglingContextTest.cpp
   SourceLocationSpecTest.cpp
   SourceManagerTest.cpp