Change assertThat(array) to allow arrays of non-nullable elements

Though array types are covariant in Java, in Kotlin they are not and this
change makes it easier to translate Java callers to Kotlin with J2KT.

RELNOTES=n/a
PiperOrigin-RevId: 608590844

core/src/main/java/com/google/common/truth/ObjectArraySubject.java

@@ -26,10 +26,9 @@
  * @author Christian Gruber
  */
 public final class ObjectArraySubject<T extends @Nullable Object> extends AbstractArraySubject {
-  private final @Nullable T @Nullable [] actual;
+  private final T @Nullable [] actual;
 
-  ObjectArraySubject(
-      FailureMetadata metadata, @Nullable T @Nullable [] o, @Nullable String typeDescription) {
+  ObjectArraySubject(FailureMetadata metadata, T @Nullable [] o, @Nullable String typeDescription) {
     super(metadata, o, typeDescription);
     this.actual = o;
   }

core/src/main/java/com/google/common/truth/StandardSubjectBuilder.java

@@ -121,7 +121,7 @@ public final IterableSubject that(@Nullable Iterable<?> actual) {
   }
 
   @SuppressWarnings("AvoidObjectArrays")
-  public final <T> ObjectArraySubject<T> that(@Nullable T @Nullable [] actual) {
+  public final <T extends @Nullable Object> ObjectArraySubject<T> that(T @Nullable [] actual) {
     return new ObjectArraySubject<>(metadata(), actual, "array");
   }
 

core/src/main/java/com/google/common/truth/Truth.java

@@ -201,7 +201,8 @@ public static IterableSubject assertThat(@Nullable Iterable<?> actual) {
   }
 
   @SuppressWarnings("AvoidObjectArrays")
-  public static <T> ObjectArraySubject<T> assertThat(@Nullable T @Nullable [] actual) {
+  public static <T extends @Nullable Object> ObjectArraySubject<T> assertThat(
+      T @Nullable [] actual) {
     return assert_().that(actual);
   }