Remove accidentally checked-in T14845.stderr

This was a stderr file for a WIP test in D4728. I ended up removing
the test, but forgot to remove the stderr file.

testsuite/tests/dependent/should_fail/T14845.stderr

-
-T14845.hs:19:16: error:
-    • Data constructor ‘MkA3’ cannot be used here
-        (it has an unpromotable context ‘Coercible a Int’)
-    • In the first argument of ‘SA’, namely ‘(MkA3 :: A Int)’
-      In the type ‘SA (MkA3 :: A Int)’
-      In the definition of data constructor ‘SMkA3’