[llvm] Rename GsymDIContext to GsymContext (PR #140227)

[Devon Loehr via llvm-commits]

DKLoehr wrote:

I'm not sure how this change could be responsible, but when trying to build chromium we're also seeing the same failure as the llvm CI above. Looking at the edit, the only thing I notice is that the include guard at the bottom of  `llvm/include/llvm/DebugInfo/GSYM/GsymContext.h` didn't match the one at the top prior to this change.

https://github.com/llvm/llvm-project/pull/140227