It should be wfLoadExtension( ‘Calendar’ ) instead per https://github.com/wikimedia/mediawiki-extensions-Calendar/blob/master/extension.json#L2
Extension talk:Calendar-Wikivoyage/Flow
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It should be wfLoadExtension( ‘Calendar’ ) instead per https://github.com/wikimedia/mediawiki-extensions-Calendar/blob/master/extension.json#L2