DOC: add pivot_table note to dropna doc (#47808)
DOC: add pivot_table note to dropna doc (#47808)

* moving edits to pivot_table

* missing punctuation'

* trailing whitespace

* clarifying documentation

* formatting

* reverting line
datapythonista/pandas,pandas-dev/pandas,pandas-dev/pandas,datapythonista/pandas,datapythonista/pandas,pandas-dev/pandas,pandas-dev/pandas,datapythonista/pandas