additional newline added to docstring when the previous line length is less than the line length limit minus 1

[DetachHead]

before

"""
87 characters ............................................................................
"""

after

"""
87 characters ............................................................................

"""

playground

https://black.vercel.app/?version=stable&state=_Td6WFoAAATm1rRGAgAhARYAAAB0L-Wj4ADOAFldAD2IimZxl1N_Wk8JgdvQ8tSq0OhVZoEptWlmdC__omMouK3ooOylgkoYGVUTpRL_A_26nUoIFOzsQcUzX_N1N5WllahS-T5qlleGaKsl1U08Mc7wSjEUdEm8AAAAADdi2bh7NF1_AAF1zwEAAADAUENLscRn-wIAAAAABFla

[veryslowcode]

I believe 4185 will fix this.

[dankrzeminski32]

I think this can be closed now that #4185 is merged.