fix: Removed an unnecessary single quotation mark in the documentation

relates to #11

wemake_python_styleguide/violations/consistency.py

@@ -2117,7 +2117,7 @@ class RawStringNotNeededViolation(TokenizeViolation):
     Forbid the use of raw strings when there is no backslash in the string.
 
     Reasoning:
-        Raw string are only needed when dealing with \' in the string.
+        Raw string are only needed when dealing with \ in the string.
 
     Solution:
         Do not prefix the string with r. Use a normal string instead.