Fix "match not match" contradiction in the description of the Find Replace plugin's "Match whole word/phrase" option

Problem/Motivation

When adding the Find Replace plugin, a typo in the description of "Match whole word/phrase" in the "configure" text contradicts itself and makes it unclear what the effect of selecting the "Match whole word/phrase" checkbox will be:
If checked, then the whole word or phrase will be matched, e.g. "book" will match not match "book" in "the book".

Steps to reproduce:

1. Go to admin/structure/feeds/tamper/list/[name-of-your-feed].
2. Click the 'Add plugin' link below a mapping.
3. Click the 'The plugin to add' dropdown.
4. Select 'Find replace' (in the 'Text' category).
5. Scroll down if necessary and read the description for the 'Match whole word/phrase' option.

Proposed resolution

Change that portion of the "Match whole word/phrase" UI text to read:
If checked, then the whole word or phrase will be matched, e.g. "book" will not match "book" in "the book".

Remaining tasks

1. Confirm that the proposed text ("not match") accurately describes the actual behavior.
2. Review the patch.

User interface changes

Change that portion of the "Match whole word/phrase" UI text to read:
If checked, then the whole word or phrase will be matched, e.g. "book" will not match "book" in "the book".

API changes

None.