docs: added an explicit note that DetectIntentRequest's text input is limited by 256 characters (#543)

* docs: added an explicit note that DetectIntentRequest's text input is limited by 256 characters

PiperOrigin-RevId: 463252698

Source-Link: googleapis/googleapis@eeacaab

Source-Link: googleapis/googleapis-gen@da3bfa0
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* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

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packages/google-cloud-dialogflow/google/cloud/dialogflow_v2/types/session.py

@@ -305,6 +305,8 @@ class QueryInput(proto.Message):
             This field is a member of `oneof`_ ``input``.
         text (google.cloud.dialogflow_v2.types.TextInput):
             The natural language text to be processed.
+            Text length must not exceed 256 character for
+            virtual agent interactions.
 
             This field is a member of `oneof`_ ``input``.
         event (google.cloud.dialogflow_v2.types.EventInput):
@@ -866,7 +868,8 @@ class TextInput(proto.Message):
         text (str):
             Required. The UTF-8 encoded natural language
             text to be processed. Text length must not
-            exceed 256 characters.
+            exceed 256 characters for virtual agent
+            interactions.
         language_code (str):
             Required. The language of this conversational query. See
             `Language