Remove the await in NmlParser/AnnotationUploadService

[fm3]

Implementing the suggestion from here https://github.com/scalableminds/webknossos/issues/7551#issuecomment-1913085950 (move the determination of hasSegmentIndex to adaptPropertiesToFallbackLayer, which happens after the NML parsing)

URL of deployed dev instance (used for testing):

• https://nmlparserremoveawait.webknossos.xyz

Steps to test:

• Download + Reupload volume annotation with and without fallback layer, should work

Issues:

• fixes #7551

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• [x] Considered common edge cases