[clang] [Tooling] Fix misleading progress report when files have multiple compile commands (PR #169640)

[Yanzuo Liu via cfe-commits]

zwuis wrote:

> ```
> [1/5] (1/1) Processing file ...
> [2/5] (1/2) Processing file ...
> [2/5] (2/2) Processing file ...
> [3/5] (1/2) Processing file ...
> ```

It seems that removing `(1/1)` (`(X/Y)`, `Y` is 1) can reduce confusion.

https://github.com/llvm/llvm-project/pull/169640