Pin to `>= process 1.6.29.0` to avoid segfaults on macos 15

**Describe the bug** On certain macos versions and toolchain, cabal segfaults because of a faulty process version. The fix is requiring the [latest version of process](https://hackage.haskell.org/package/process) **To Reproduce** - macos version 15 - command line sdk that can compile for macos 26 - any process version that 1. is configured to support `posix_spawn` 2. is older than the latest version 1.6.29.0 **Expected behavior** cabal should not segfault. **System information** - Operating system: macos version 15 - `cabal`, `ghc` versions: n/a **Additional context** I'm not opening an MR since I'm not sure about the fix exactly. It's possible that it's not worth requiring that new of a process version because of version conflicts.