simplify invoking create_manpage_completions.py

My previous change to avoid creating a *.pyc file when running
create_manpage_completions.py was wrong because I put the
`sys.dont_write_bytecode = True` on the wrong line. Rather than simply
move that statement make the simpler, cleaner, fix that removes the need
for `eval` where that program is invoked.

share/functions/fish_update_completions.fish

@@ -1,4 +1,4 @@
 function fish_update_completions --description "Update man-page based completions"
 	# Clean up old paths
-	eval (string escape $__fish_datadir/tools/create_manpage_completions.py) --manpath --progress --cleanup-in '~/.config/fish/completions' --cleanup-in '~/.config/fish/generated_completions'
+	python -B $__fish_datadir/tools/create_manpage_completions.py --manpath --progress --cleanup-in '~/.config/fish/completions' --cleanup-in '~/.config/fish/generated_completions'
 end

share/tools/create_manpage_completions.py

@@ -20,7 +20,6 @@ THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND
 import string, sys, re, os.path, bz2, gzip, traceback, getopt, errno, codecs
 from deroff import Deroffer
 
-sys.dont_write_bytecode = True
 lzma_available = True
 try:
     try:

share/tools/deroff.py

@@ -3,10 +3,8 @@
 
 """ Deroff.py, ported to Python from the venerable deroff.c """
 
-
 import sys, re, string
 
-sys.dont_write_bytecode = True
 IS_PY3 = sys.version_info[0] >= 3
 
 class Deroffer: