Revert "Remove usage of to-be-deprecated Throwables"

Guava snapshot is gone.

This reverts commit 8df8a2489d.

Change-Id: I1f6f40a824e39240d67da9b305bdc8144505e7bf

gerrit-server/src/main/java/com/google/gerrit/server/util/RequestScopePropagator.java

@@ -129,7 +129,7 @@ public abstract class RequestScopePropagator {
           try {
             wrapped.call();
           } catch (Exception e) {
-            Throwables.throwIfUnchecked(e);
+            Throwables.propagateIfPossible(e);
             throw new RuntimeException(e); // Not possible.
           }
         }