The support for the Angika language was added in 2011 in this commit: https://gerrit.wikimedia.org/r/plugins/gitiles/mediawiki/core/+/014647a04adba321c2014bbe791baf766d8c1278

It's unclear why the autonym was written as "अङ्गिका" back then. The original request was for the name "अंगिका". This name also appears in Ethnologue, and it makes sense.

The correction was requested in translatewiki: https://translatewiki.net/wiki/Thread:Support/How_to_replace_wrongly_translated_spelling_of_a_word_appearing_in_language_list