variable-length-quantity: Remove nonstandard properties from 'metadata.yml'
variable-length-quantity: Remove nonstandard properties from 'metadata.yml'

As discussed in exercism/x-common#597, there is not reason
to keep information about deprecation or exercise classification
in that file.

kgengler/x-common,Vankog/problem-specifications,rpottsoh/x-common,rpottsoh/x-common,jmluy/x-common,petertseng/x-common,Vankog/problem-specifications,kgengler/x-common,jmluy/x-common,jmluy/x-common,ErikSchierboom/x-common,ErikSchierboom/x-common,exercism/x-common,petertseng/x-common,exercism/x-common