fixed merge conflict

Author: olavloite

google-cloud-clients/google-cloud-spanner/src/main/java/com/google/cloud/spanner/TransactionRunnerImpl.java

@@ -23,7 +23,6 @@
 
 import com.google.api.client.util.BackOff;
 import com.google.cloud.Timestamp;
-import com.google.cloud.spanner.SpannerImpl.AbstractReadContext;
 import com.google.cloud.spanner.SpannerImpl.SessionImpl;
 import com.google.cloud.spanner.SpannerImpl.SessionTransaction;
 import com.google.cloud.spanner.spi.v1.SpannerRpc;