Auto merge of #13988 - dsprenkels:tidy-fncalls, r=Wafflespeanut

test-tidy: Check for space between function name and `(`

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Disallow an extraneous space in a function call between
the function name and the opening parenthesis in Rust
code, while ignoring macro declarations.

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- [x] `./mach build -d` does not report any errors
- [x] `./mach test-tidy --all` does not report any errors
- [x] `./mach test-tidy --self` does not report any errors
- [x] These changes fix #13980

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- [x] There are tests for these changes, these are written in
 - `python/tidy/servo_tidy_tests/rust_tidy.rs`
 - `python/tidy/servo_tidy_tests/test_tidy.py`
- [ ] These changes do not require tests

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