Fix typo in class name `AbstractInterfanceChange`

[millie-crowther]

The class name should be AbstractInterfaceChange, not AbstractInterfanceChange

graphql-schema-diff/schemadiff/changes/interface.py

Line 45 in 3382073

class AbstractInterfanceChange(Change):

[millie-crowther]

Pull request to fix is here #25

[mattiabaldari]

I guess this can be closed