No, a spell cast by Wish does not require anything
First, the breakdown of what requirements are in a spell using sources from the PHB.
What attributes are considered spell requirements?
Here's the important bit from Wish, emphasis mine:
any requirements in that spell
Does your spell cost an action to cast? A bonus action? A reaction? How about 1 minute to cast? An hour? 24 Hours? None of this matters. You don't need to meet any requirements. Is the creature or object way out of the spells range? What if the creature doesn't match the spells description for it to be a valid target? None of that matters either, you don't need to meet any requirements.
Since Wish ignores the requirements in a spell, and concentration by definition falls within the spell, Wish would ignore it as well. Concentration is not separate and distinct, it is a core requirement of the spell in question. Since Wish ignores requirements, concentration is no longer a factor.
It would make very little sense for Wish to ignore the sections labelled Casting Time, Range, Components, but then for some reason have an arbitrary distinction about Duration. If it wasn't meant to apply to everything within the spell, it wouldn't say that it does.
Wish is a spell with something very important in its description:
Wish is the mightiest spell a mortal creature can
cast. By simply speaking aloud, you can alter the very
foundations of reality in accord with your desires.
Duplicating a spell is its basic function, but it does so without needing to meet any requirements in said spell. You can cast Wall of Ice in midair with Wish. You can cast Awaken on a creature with the monster type. You can cast Planar Binding on a Bear. None of the spell requirements matter anymore. As Wish states, it simply takes effect.
It wouldn't be Wish if you weren't altering reality with it. That's the very first thing in the spells effect, and it's not exclusive to the 2nd part of the spell, or it would preface that instead of the entire text. And if it wasn't all inclusive, the wording would have stated that you don't need to meet any requirements to cast the spell. Since it specifies in instead, it's all inclusive.
Finally, there's also something that I've been overlooking. You are not casting a lower level spell when you cast Wish. You are casting Wish. One of the uses of Wish is to effectively duplicate a lower level spell, while ignoring any of the requirements in that spell.
Since Wish does not state you are casting a second spell, concentration is not required to sustain the duplicate effect because the duration of Wish is instantaneous. More importantly, you aren't responsible for sustaining the second spell, Wish is, that's its function. If somebody were trying to dispel the effects of a spell duplicated by Wish, they would be countering a level 9 conjuration spell regardless of the level or school the spell was effectively cast at. The reason for this brings us full circle back to the initial casting. You are not casting the 8th level spell or lower, you are casting a 9th level spell called Wish which can duplicate any 8th level spell or lower as its basic function, devoid of any requirements in the spell it duplicates.