docs: update docstring of to_json() method (#511)
from #494,
this PR updated the docstring of ``to_json`` method in the credential so that it points user to ``from_authorized_user_info`` instead of the non-existent ``from_json``
diff --git a/google/oauth2/credentials.py b/google/oauth2/credentials.py
index d39848b..7572196 100644
--- a/google/oauth2/credentials.py
+++ b/google/oauth2/credentials.py
@@ -300,8 +300,9 @@
generated JSON.
Returns:
- str: A JSON representation of this instance, suitable to pass to
- from_json().
+ str: A JSON representation of this instance. When converted into
+ a dictionary, it can be passed to from_authorized_user_info()
+ to create a new credential instance.
"""
prep = {
"token": self.token,