clarified misleading wording about squashing commits

The HEAD~2 above is shorthand for two latest commits. The above command

will open an editor showing the two commits, prefixed with the word "pick".

Change the second line to "squash" instead. This will keep the

Change "pick" on the second line to "squash" instead. This will keep the

first commit, and squash the second commit into the first one. Save and quit

the editor. A second editor window should open, so you can reword the

commit message for the commit now that it includes both your steps.