Incomplete doc in deutils

A line is complete in docs in _desolve in deutils. It can be more than one thing possible there. I need suggestions to complete this sentence.
Completed the doc sentence of _desolve in deutils.py

The sentence, This is useful when the function, was incomplete earlier. It is now replaced with `This is useful when the expression has more than one function in it.`
Merge pull request #7657 from KDMOE/typo_deutils_desolve

Incomplete doc in deutils [skip ci]