Facets should not be arrays

[sschuberth]

There is e.g.

curated-data/curations/maven/mavencentral/com.google.code.gson/gson.yaml

Lines 10 to 11 in f3a9ef4

	dev: []
	tests: []

but according to both the spec and this test, facets should not be arrays (but structures).

[sschuberth]

Somewhat related, sometimes facets are also strings:

curated-data/curations/maven/mavencentral/io.netty/netty-buffer.yaml

Line 11 in f3a9ef4

- buffer/**

[ariel11]

@nellshamrell - should this issue be moved to the website repo, maybe?

[sschuberth]

@ariel11, IMO this is a data issue and thus correctly placed here.

[nellshamrell]

@ariel11 Let's leave it here for now