Make the emoticon list a raw string (#4139)

While working on an unrelated task I got warnings about an unsupported
escape sequence (`"\("`) in the tokenizer exceptions. Making the
tokenizer exceptions a raw string makes this warning go away.

The specific string that triggered this is `¯\(ツ)/¯`.

spacy/lang/tokenizer_exceptions.py

@@ -109,7 +109,7 @@
 
 
 emoticons = set(
- """
+ r"""
 :)
 :-)
 :))