This function has been deprecated. Use Reader themes instead of old legacy AMP post templates.
Add hooks to use legacy AMP post templates from before v0.4.
If you want to use the template that shipped with v0.3 and earlier, you can use this to force that. Note that this may not stick around forever, so use caution and
Note that the old legacy post templates from AMP plugin v0.3 should no longer be used. Update to using the current AMP legacy post templates or better yet switch to using a full Reader theme.