Allow usages of java.util.Objects.requireNonNull in the backport.

Relevant to #5269 in that it's an exception -- a case in which we *are* willing to use a Java 7 API because we know this particular API is safe to use under Android.

RELNOTES=n/a
PiperOrigin-RevId: 364567470

android/guava/pom.xml

@@ -151,6 +151,12 @@
       <plugin>
         <groupId>org.codehaus.mojo</groupId>
         <artifactId>animal-sniffer-maven-plugin</artifactId>
+        <configuration>
+          <ignores>
+            <!-- Allow requireNonNull: Android desugaring rewrites it (so it's safe for us to use), and it's useful for null checks. Note that this line allows *all* methods from java.util.Objects. That's the best that we can do with the configuration options that Animal Sniffer offers. -->
+            <ignore>java.util.Objects</ignore>
+          </ignores>
+        </configuration>
       </plugin>
       <plugin>
         <artifactId>maven-javadoc-plugin</artifactId>