gh-91276: revert the increase of dis output width (GH-92126)

Author: iritkatriel

Lib/dis.py

@@ -264,7 +264,7 @@ def show_code(co, *, file=None):
 _ExceptionTableEntry = collections.namedtuple("_ExceptionTableEntry",
     "start end target depth lasti")
 
-_OPNAME_WIDTH = max(map(len, opmap))
+_OPNAME_WIDTH = 20
 _OPARG_WIDTH = 5
 
 class Instruction(_Instruction):