[clang] [clang-repl] [test] Make an XFAIL more precise (PR #70991)

[via cfe-commits]

dyung wrote:

> > > If you still need help reproducing or debugging the issue on our bot, please let me know.
> > 
> > 
> > Thanks, much appreciated. Can you test if [mstorsjo at clang-repl-xfail](https://github.com/mstorsjo/llvm-project/commit/clang-repl-xfail) seems to run correctly in this environment? Otherwise I'll try to push it tomorrow and see how it fares on the bot.

It failed, but due to a typo in the XFAIL you added:
```
target={{.*}-ps4, target={{.*}-ps5
```
These should have balanced braces. If I add the missing braces, the test passes with an XFAIL on the bot.

https://github.com/llvm/llvm-project/pull/70991