Test another remove_child method

[douweschulte]

There is a method that does exactly what the implementation in remove_child_by does, so it could be that this is faster, in which case it should be used. If it is equal use this method as well, because it is cleaner.

[douweschulte]

I tested the currrent method against the vector.retain build in method and the later one proved ~+75% faster both on small and big test subjects. So the build in method will be used.

Benchmark: Remove - small average time over 53158 runs:
        53μs 991ns ± 11μs 631ns

Benchmark: Retain - small average time over 98754 runs:
        30μs 944ns ± 7μs 455ns

Benchmark: Remove - big average time over 374 runs:
        7ms 252μs ± 615μs 642ns

Benchmark: Retain - big average time over 716 runs:
        4ms 180μs ± 270μs 128ns

Remove: the build in method
Retain: using the vector.retain function
Small: 1ubq.pdb
Big: pTLS-6484.pdb