Add WhatsNew API entry for parse_math

Author: aitikgupta

doc/api/next_api_changes/behavior/20367-AG.rst

@@ -0,0 +1,12 @@
+``Text``
+~~~~~~~~
+
+``Text`` objects now allow a **parse_math** keyword-only argument
+which defaults to True. When it is passed as False, that text object
+will consider the string as a literal and will not try to parse it
+as a mathtext object.
+
+``TextBox``
+-----------
+``TextBox`` now defaults its text object's **parse_math** argument
+as False.