Fix ErrorProne reported error [EmptyBlockTag]

Change-Id: I1e6666a241d3af43f4e1dd9f00bab0899d529b61

src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerRefDatabase.java

diff --git a/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerRefDatabase.java b/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerRefDatabase.java
index ad6655b..8db7745 100644
--- a/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerRefDatabase.java
+++ b/src/main/java/com/googlesource/gerrit/plugins/spannerrefdb/SpannerRefDatabase.java
@@ -101,7 +101,6 @@
    * @param expectedValue - the expected value to be found in the global-refdb
    * @param newValue - the new value to put in the global-refdb if the expectedValue is present
    * @return success
-   * @throws GlobalRefDbSystemError
    */
   private boolean doCompareAndPut(
       Project.NameKey project, String refName, String expectedValue, String newValue)