fix indentation for note block in calling.rst (celery#5933)

Author: imomaliev

CONTRIBUTORS.txt

@@ -275,3 +275,4 @@ Shashank Parekh, 2019/07/11
 Arel Cordero, 2019/08/29
 Kyle Johnson, 2019/09/23
 Dipankar Achinta, 2019/10/24
+Sardorbek Imomaliev, 2020/01/24

docs/userguide/calling.rst

@@ -449,13 +449,13 @@ json -- JSON is supported in many programming languages, is now
 
     .. note::
 
-      (From Python official docs https://docs.python.org/3.6/library/json.html)
-      Keys in key/value pairs of JSON are always of the type :class:`str`. When
-      a dictionary is converted into JSON, all the keys of the dictionary are
-      coerced to strings. As a result of this, if a dictionary is converted
-      into JSON and then back into a dictionary, the dictionary may not equal
-      the original one. That is, ``loads(dumps(x)) != x`` if x has non-string
-      keys.
+        (From Python official docs https://docs.python.org/3.6/library/json.html)
+        Keys in key/value pairs of JSON are always of the type :class:`str`. When
+        a dictionary is converted into JSON, all the keys of the dictionary are
+        coerced to strings. As a result of this, if a dictionary is converted
+        into JSON and then back into a dictionary, the dictionary may not equal
+        the original one. That is, ``loads(dumps(x)) != x`` if x has non-string
+        keys.
 
 pickle -- If you have no desire to support any language other than
     Python, then using the pickle encoding will gain you the support of