Remove "ExtensionRegistry::getInstance()->getAllThings();"

[mwjames]

[0] adds access to the version number without requiring access to [1]:

$extensionData = ExtensionRegistry::getInstance()->getAllThings();
if ( isset( $extensionData['Semantic Glossary'] ) ) {
	return $extensionData['Semantic Glossary']['version'];
}

[0] https://phabricator.wikimedia.org/T151136
[1] https://github.com/SemanticMediaWiki/SemanticGlossary/blob/master/SemanticGlossary.php#L47-L54

[kghbln]

[0] https://phabricator.wikimedia.org/T151136

Was resolved in the meantime so fluff is expected for 1.29+ however we still have 1.27 LTS