#Your DM will have to make a ruling on this since the rules don't say
There are no rules on how to measure the distance between one dimension and another which makes sense because even the concept of trying to do so is pretty much nonsense. Thus, there is no defined distance between the two according to the rules and your DM will have to make a ruling on whether they will count extradimensional places as being further than 100 feet away or if they consider that is does not count. It is also worth noting that this ruling would also apply to any other extradimensional storage such as a portable hole or handy haversack.
However, it really shouldn't matter which one your DM chooses in the vast majority of cases. It is trivial for a warlock to summon their weapon and as they do it once a day the issue won't ever come up. As an adventurer, it seems unlikely that they would not already be meeting or exceeding this.