Describe the bug

When using the :active prop on a single B-Tab which is routed to a method to return a boolean, the returned result is ignored or not applied once the DOM is rendered.
The first tab in the index is the one that always remains active in the DOM (highlighted) regardless of the :active prop.

Steps to reproduce the bug

1. Go to https://jsfiddle.net/qL0ao8yh/
2. Hit run
3. "test1 (inactive)" is selected, whereas "test2 (active)" should be selected as this has the active prop set to true.

Expected behavior

"test2 (active)" should be the default highlighted tab as this is set to "active:true" in the data model.

Versions

Libraries:

• BootstrapVue: 2.21.0
• Bootstrap: 4.5.3
• Vue: 2.6.12

Environment:

• Device: Laptop/Computer
• OS: Ubuntu 20.04.1 LTS (64 bit)
• Browser: Chrome
• Version 87.0.4280.88 (Official Build) (64-bit)

Demo link

BROKEN as of BoostrapVue 2.21.0: https://jsfiddle.net/qL0ao8yh/
WORKING on BoostrapVue 2.20.1: https://jsfiddle.net/u1esL50n/

The code between these two JSFiddles are identical, the only difference being the BootstrapVue version.

I believe this is the breaking change: #6154