It depends on the repository settings. If you have write access (and note the person who opens the PR appears to be a member of Apache, so I'm assuming they have write access), the default settings in Github allow merging even without approval, or with requested changes. (I.e., the defaults are pretty lax; you have to enable the "requires approval to merge" stuff.)
Even if approval is required, anyone with admin access can override the lack of approval. (For that user, the merge button is a different color/state: it very clearly warns you when you exercise that right.) I don't think it's clear which is the case here.
(But also note that there is an approval, in addition to the "changes requested". So, even in the scenario that approval is required, the PR could be merged, technically, but it would require dismissing the requested changes in that case, which was not done here.)
Even if approval is required, anyone with admin access can override the lack of approval. (For that user, the merge button is a different color/state: it very clearly warns you when you exercise that right.) I don't think it's clear which is the case here.
(But also note that there is an approval, in addition to the "changes requested". So, even in the scenario that approval is required, the PR could be merged, technically, but it would require dismissing the requested changes in that case, which was not done here.)