removed file test/em_real/namelist.input_default (wrf-model#1900)

TYPE: no impact

KEYWORDS: namelist.input_default, remove file, delete

SOURCE: internal

DESCRIPTION OF CHANGES:
Problem: The file test/em_real/namelist.input_default is probably more confusing than helpful since users may think that's the one they should use, instead of just namelist.input.

Solution:
Removed the file altogether

LIST OF MODIFIED FILES:
D test/em_real/namelist.input.default

TESTS CONDUCTED:

No tests necessary. Just removed a text file

Author: kkeene44