[clang] Mark the file opened by DeserializedDeclsSourceRangePrinter as a text file (PR #135842)

[Zibi Sarbinowski via cfe-commits]

zibi2 wrote:

The 2 failing checks above don't seem to be related and they happen in other PRs. I'm going to merge this in.

https://github.com/llvm/llvm-project/pull/135842