[bigtable/test-proxy]: version used for google-cloud-bigtable is not consistent

[zhumin8]

These two versions are not consistent even though their link points to the same record in versions.txt.

google-cloud-java/java-bigtable/test-proxy/pom.xml

Lines 12 to 20 in 32b4eb8

	<parent>
	<artifactId>google-cloud-bigtable-parent</artifactId>
	<groupId>com.google.cloud</groupId>
	<version>2.79.0-SNAPSHOT</version><!-- {x-version-update:google-cloud-bigtable:current} -->
	</parent>
	<properties>
	<bigtable.client.version>2.78.1</bigtable.client.version><!-- {x-version-update:google-cloud-bigtable:current} -->
	</properties>

likely missed in this manual bump
ca594e4#diff-981ea28a9f3ed96a3e5bf9dcc1c760d822eab6bab680e6874bc4df96331c700a