OneOf is set multiple times with different values

These calls to OneOf setters in `BigtableTableAdminClientWrapper.java` overwrite previously set values:

https://github.com/googleapis/java-bigtable-hbase/blob/d3403e14cf0463d39e71d1af62a81f3c4110d125/bigtable-client-core-parent/bigtable-client-core/src/main/java/com/google/cloud/bigtable/grpc/BigtableTableAdminClientWrapper.java#L240

https://github.com/googleapis/java-bigtable-hbase/blob/d3403e14cf0463d39e71d1af62a81f3c4110d125/bigtable-client-core-parent/bigtable-client-core/src/main/java/com/google/cloud/bigtable/grpc/BigtableTableAdminClientWrapper.java#L258

This was noticed because of an [Error Prone static check](https://errorprone.info/bugpattern/RedundantSetterCall), which reports the following error for that code:

```
src/main/java/com/google/cloud/bigtable/grpc/BigtableTableAdminClientWrapper.java:240: error: [RedundantSetterCall] The oneof `Target` (set via setDeleteAllDataFromTable, setRowKeyPrefix) was called twice with . Setting the same field multiple times is redundant, and could mask a bug.
.setRowKeyPrefix(rowKeyPrefix)
^
(see https://errorprone.info/bugpattern/RedundantSetterCall)
src/main/java/com/google/cloud/bigtable/grpc/BigtableTableAdminClientWrapper.java:258: error: [RedundantSetterCall] The oneof `Target` (set via setDeleteAllDataFromTable, setRowKeyPrefix) was called twice with . Setting the same field multiple times is redundant, and could mask a bug.
.setRowKeyPrefix(rowKeyPrefix)
^
(see https://errorprone.info/bugpattern/RedundantSetterCall)
```

Start in bigtable-client-core-parent/bigtable-client-core/src/main/java/com/google/cloud/bigtable/grpc/BigtableTableAdminClientWrapper.java at the calls near lines 240 and 258. Read the surrounding OneOf target construction and run the Error Prone RedundantSetterCall check. Done means the redundant setter warnings are resolved without changing the intended target behavior.

Scritto dal modello di indicizzazione a partire dal testo della issue.