fix(java): syncing java and android snippets

[paulsmithkc]

Fixes #876 ☕️

[snippet-bot]

Here is the summary of possible violations 😱

There is a possible violation for not having product prefix.

• samples/snippets/src/main/java/com/example/firestore/snippets/model/City.java:23, tag fs_class_definition

The end of the violation section. All the stuff below is FYI purposes only.

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Here is the summary of changes.

You are about to add 2 region tags.

• samples/snippets/src/main/java/com/example/firestore/snippets/model/City.java:23, tag fs_class_definition
• samples/snippets/src/main/java/com/example/firestore/snippets/model/City.java:24, tag firestore_data_custom_type_definition

You are about to delete 1 region tag.

• samples/snippets/src/main/java/com/example/firestore/snippets/model/City.java:32, tag firestore_data_custom_type_definition

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[paulsmithkc]

Snippet tags were moved to cover the entire class. See #876 and firebase/snippets-android#322

[meredithslota]

We will need to re-remove the obsolete region tag fs_class_definition after this is merged, but it is easy to do.