allow "https://bqgazetteer.bethmardutho.org" for @resp attribute

[wlpotter]

the @resp attribute, which is now allowed on both tei:placeName and tei:location elements, should allow the attribute value to be the string "https://bqgazetteer.bethmardutho.org". For tei:location elements, this seems to be true. However, on tei:placeName elements, @resp="https://bqgazetteer.bethmardutho.org" is invalid (the schema expects only the string "http://syriaca.org")

@dlschwartz this change may already have been made, but we likely only want this in the BQG schema. Perhaps revert the change in the main schema but keep this issue open as a reminder of the changes we need to make for the final BQG-specific schema?

Cf. this commit, which likely included this change.

[dlschwartz]

This attribute value has been removed from the place schema but can be added back into the bqg-specific schema.