The Rambam actually says something which is somewhat the opposite - you could be an apikorus for refusing to accept that the literal interpretation is not what the Torah means.
The Rambam's third principle of faith is believing that Hashem does not have a body. The Rambam in Moreh Nevochim 2:25 actually says that he would have had an easier time reinterpreting the account of Bereishis to align with Aristotle's view of the eternity of existence than he did with reinterpreting all of the references to G-d's having a body to be in line with G-d's incorporeality. It is a principle of faith to not read these verses according to the simplest way to read them.
In fact, the Rambam there writes that he does not feel that reinterpreting these verses to align with Aristotle's view would be a problem with reading the verses, and his rejection of Aristotle's view is not because of the text of Bereishis. It would have been a valid way to read it, if not for the fact that the Rambam has other, very significant, issues with the doctrine that is behind it.
So not reading something according to it's literal reading is certainly not an independent reason to be considered a heretic. And the Rambam would have been willing to reinterpret these very same verses, albeit for a different purpose.