Eliminate redundant double is_function test

When tuple funs were still supported, the idiom for allowing
real funs with a certain arity but not tuple funs was:

  is_function(Fun) andalso is_function(Fun, Arity)

The reason that both tests were needed is because:

  is_function({M,F}) would return 'false'
  is_function({M,F}, Arity) would return 'true'

In 53ec991d19, is_function/2 was updated to only return 'false'
for tuples, so the call to is_function/1 can be removed.

0 files changed, 0 insertions, 0 deletions