Avatar should use full-size instead of thumb

[r-a-y]

Forgot to port over some logic to use the full-size avatar when the requested size is larger than the BP thumb width during the refactoring to use the 'get_avatar_data' filter.

This is a regression since #7424.

See:
​https://buddypress.org/support/topic/buddypress-avatars-are-blurry-for-post-authors/

[DJPaul]

Not tested but if this is a fix, let's get it in ASAP. Let's spend next week fixing things for 2.9.1, and release on the subsequent Monday.

[r-a-y]

In 11669:

Avatars: If requested width is larger than our thumb width, set avatar size to 'full'.

After r11614, fixes a regression where avatars might appear blurry when
fetching a post author's avatar.

Props coach-afrane.

Fixes #7578 (2.9-branch).

[r-a-y]

In 11670:

Avatars: If requested width is larger than our thumb width, set avatar size to 'full'.

After r11614, fixes a regression where avatars might appear blurry when
fetching a post author's avatar.

Props coach-afrane.

Fixes #7578 (trunk).