Metrics: Newlines are counted as characters

> New lines are treated as characters in the character count on macOS but not iOS.

> To reproduce, just open a new note and hit Enter a couple of times — the Metrics UI in the top-right corner will show a count corresponding to the number of Enter presses.

h/t @guarani (Thank you Paul!!)

Start by reproducing the issue in the Metrics UI at the top-right of a new note, then locate the macOS character-count implementation. Compare its newline handling with the iOS behavior described in the report. Done means pressing Enter no longer increases the macOS character count unexpectedly.

Written by the indexing model from the issue text.