Bug 21866: Changed "report" to "plugins" for the warning "This report was written...

Bug 21866: Changed "report" to "plugins" for the warning "This report was written for an older version of Koha. Run at your own risk"

To find this change:

1. Enable use plugins in global system preferences
2. Go to tools then click tool plugins
3. Verify that this string now says plugins

Signed-off-by: Owen Leonard <oleonard@myacpl.org>
Signed-off-by: Kyle M Hall <kyle@bywatersolutions.com>
Signed-off-by: Nick Clemens <nick@bywatersolutions.com>
(cherry picked from commit 5e2e101037bb2bfb8579fcee331388e56658db84)
Signed-off-by: Martin Renvoize <martin.renvoize@ptfs-europe.com>