Bikeshedding means talking (or even arguing) about a small detail instead of a larger issue at hand. If you imagine building a house and having a bike shed outside, it would be akin to angsting over the color and fun name for the bike shed instead of working on actually finishing the house. At the end of the day, you won't have a place to live because you were lost in details that didn't matter.
In the wild
I'm approving this change because it is timely and needed, and because as a rule, we should avoid bikeshedding as a reason to withhold approval.
In the above statement, they recognize that approving changes can be delayed because of getting distracted by details, and given the urgency and need of the change, are pointing out that this should be avoided.