_metatag_is_entity_route_entity static cache problematic

Problem/Motivation

I am using Tome (contrib module) to produce a static version of our site. One characteristic of Tome is that it will process several requests per bootstrap of Drupal. The usage of static in _metatag_is_entity_route_entity causes an issue because it cannot be reset between requests (within a bootstrap) - I need to switch it to Drupal static as it is resettable

Steps to reproduce

Hard to reproduce without doing multiple requests per bootstrap.

Proposed resolution

Use drupal_static not static.

Remaining tasks

Just that.

User interface changes

None.

API changes

None.

Data model changes

None.