docs: make delete examples consistent with other languages

[billyjacobson]

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Fixes #<issue_number_goes_here> ☕️

If you write sample code, please follow the samples format.

[snippet-bot]

Here is the summary of changes.

You are about to add 3 region tags.

• samples/snippets/src/main/java/com/example/bigtable/deletes/DeleteFromColumnExample.java:19, tag bigtable_delete_from_column
• samples/snippets/src/main/java/com/example/bigtable/deletes/DeleteFromColumnFamilyExample.java:19, tag bigtable_delete_from_column_family
• samples/snippets/src/main/java/com/example/bigtable/deletes/DeleteFromRowExample.java:19, tag bigtable_delete_from_row

You are about to delete 2 region tags.

• samples/snippets/src/main/java/com/example/bigtable/deletes/DeleteColumnCellsExample.java:19, tag bigtable_delete_from_column
• samples/snippets/src/main/java/com/example/bigtable/deletes/DeleteRowExample.java:19, tag bigtable_delete_from_row

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[kolea2]

lgtm with one suggestion