Inconsistent warning message when there are ignored header tags

[ironprogrammer]

For ​Classic Editor, there are 6 tags defined in the header:

gutenberg, disable, disable gutenberg, editor, classic editor, block editor

However, after the latest plugin update, the following notice is now visible on the plugin page, which indicates that 2 of the 6 tags were ignored:

During the last import of your plugin the following warnings were encountered. This message is visible only to the plugin authors & committers.
One or more tags were ignored: classic editor, block editor. Please limit your plugin to 5 tags.

Additionally, the "tag cloud" has 5 terms, including classic editor, which the notice erroneously warns was ignored:

It is expected that the warning message matches the ignored tags/count.

[dd32]

In 13475:

Plugin Directory: Readme Validator: Fix an off-by-one in the readme validator for number of ignored tags.

Props ironprogrammer.
Fixes #7559.