MoreAssert: Suppress warning about unchecked conversion

Suppress it in the same way that we do in core Gerrit (see
change I4a774846a).

Change-Id: I44cbbfde6ca2ec34dd4421e1c9d41a8a134e13b3

javatests/com/google/gitiles/MoreAssert.java

diff --git a/javatests/com/google/gitiles/MoreAssert.java b/javatests/com/google/gitiles/MoreAssert.java
index bd80d69..3f79874 100644
--- a/javatests/com/google/gitiles/MoreAssert.java
+++ b/javatests/com/google/gitiles/MoreAssert.java
@@ -24,7 +24,9 @@
       throw new AssertionError("Expected " + expected.getSimpleName() + " to be thrown");
     } catch (Throwable actual) {
       if (expected.isAssignableFrom(actual.getClass())) {
-        return (T) actual;
+        @SuppressWarnings("unchecked")
+        T toReturn = (T) actual;
+        return toReturn;
       }
       throw new AssertionError(
           "Expected " + expected.getSimpleName() + ", but got " + actual.getClass().getSimpleName(),