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/project/RefPattern.java

@@ -49,7 +49,7 @@ public class RefPattern {
       try {
         return exampleCache.get(refPattern);
       } catch (ExecutionException e) {
-        Throwables.throwIfUnchecked(e.getCause());
+        Throwables.propagateIfPossible(e.getCause());
         throw new RuntimeException(e);
       }
     } else if (refPattern.endsWith("/*")) {