Fix invalid escape sequences in regex (#1814)

esphome/components/logger/__init__.py

@@ -205,8 +205,7 @@ def maybe_simple_message(schema):
 
 def validate_printf(value):
     # https://stackoverflow.com/questions/30011379/how-can-i-parse-a-c-format-string-in-python
-    # pylint: disable=anomalous-backslash-in-string
-    cfmt = """\
+    cfmt = r"""
     (                                  # start of capture group 1
     %                                  # literal "%"
     (?:[-+0 #]{0,5})                   # optional flags