fix attribute completeness description text

[JanReifenrath]

The attribute completeness description text says "attributes" even if there is only a single attribute selected. It should only say "attribute"

[JanReifenrath]

the code should look roughly like this if len(self.attribute_names) > 1: tags = "attributes " + ", ".join(self.attribute_names) else: tags = "attribute " + self.attribute_names[0]

[Gigaszi]

hey @JanReifenrath , didnt you already fix this or do i remember wrong?

[JanReifenrath]

yes, this has already been fixed (link to commit where it got fixed: https://github.com/GIScience/ohsome-quality-api/commit/3bfb2d5780dd29e9fe310a5bbe8be431e158f23f )