Translate: migrate published v3 translate batch samples [(#2914)](Goo…

…gleCloudPlatform/python-docs-samples#2914)

* Translate: migrate published b v3 tch samples

* added missing requirements

* extended wait time

* inlined some vals and specified input and output

* added link to supported file types & modified default values of input uri

* fixed small nit

samples/snippets/requirements.txt

@@ -1,2 +1,3 @@
+google-cloud-translate==2.0.0
 google-cloud-automl==1.0.1
 google-cloud-storage==1.29.0