docs: Update SimpleApp to explicitly set project id

[PhongChuong]

When running in Google Cloud console, the default google cloud project might not be set leading to 404 errors. This update requires the reader to explicitly set the project value.

This also removes the explicit use of UUID to set jobId as the library now internally generates the value.

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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/bigquery/SimpleApp.java:44, tag bigquery_simple_app_client
• samples/snippets/src/main/java/com/example/bigquery/SimpleApp.java:47, tag bigquery_simple_app_query
• samples/snippets/src/main/java/com/example/bigquery/SimpleApp.java:77, tag bigquery_simple_app_print

You are about to delete 3 region tags.

• samples/snippets/src/main/java/com/example/bigquery/SimpleApp.java:36, tag bigquery_simple_app_client
• samples/snippets/src/main/java/com/example/bigquery/SimpleApp.java:39, tag bigquery_simple_app_query
• samples/snippets/src/main/java/com/example/bigquery/SimpleApp.java:70, tag bigquery_simple_app_print

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[whuffman36]

LGTM