Update Receipt language for Offline Donation Instructions to match other instances

[mathetos]

Issue Overview

We refer to the Offline Donations Instructions in several different ways. It would be more efficient and easier for translators if we referred to it the same way every time.

Current Behavior

On the receipt we currently have this: esc_html_e( 'Offline Payment Instruction:', 'give' ); found here

It uses "Payment", has a colon, and is singular.

But all other instances are like this:
__( 'Offline Donation Instructions', 'give' ), using "Donation" instead of "Payment", does not have a colon, and is plural.

Possible Solution

Update the line above to be:
esc_html_e( 'Offline Donations Instructions', 'give' );

But I'm not sure how to handle the colon correctly in this case, unless it was outside the string, but then I think it would have problems with RTLs.