Add master/slave to misused terms

Why is this change being made?

This MR adds master/slave to the misused terms list since they refer to the practice of slavery.

I've proposed here to replace them with primary/secondary, but other alternative words are main/replica (or the combos main/secondary or primary/replica), or other options not listed here. I don't have strong opinions on what we recommend as the replacement.

Author Checklist

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