Don't change log level for Corefile._parse_stack()

If we don't want to see the log, don't print it. There are no spammy
debug logs anymore.

Fixes Gallopsled#1666

pwnlib/elf/corefile.py

@@ -666,7 +666,7 @@ def __init__(self, *a, **kw):
                     log.warn('Could not find the stack!')
                     self.stack = None
 
-            with context.local(bytes=self.bytes, log_level='warn'):
+            with context.local(bytes=self.bytes):
                 try:
                     self._parse_stack()
                 except ValueError: