LatinBackoffLemmatizer fails on words with -aris ending

[TylerKirby]

Describe the bug
The LatinBackoffLemmatizer seems to fail on words with -aris ending.

To Reproduce

from cltk.lemmatize.lat import LatinBackoffLemmatizer
lemmatizer = LatinBackoffLemmatizer()
lemmatizer.lemmatize(["abundaris"])
Out[7]: [('abundaris', 'abundaris')]
lemmatizer.lemmatize(["amaris"])
Out[8]: [('amaris', 'amaris')]
lemmatizer.lemmatize(["duraris"])
Out[9]: [('duraris', 'duraris')]
lemmatizer.lemmatize(["crearis"])
Out[10]: [('crearis', 'crearis')]

Expected behavior
E.g., amaris should lemmatize to amo.

Desktop (please complete the following information):

• OS and version: MacOS 11.5.1
• cltk version 1.0.18