Fix J2ObjC retain-cycle in LinkedListMultimap:

```
(192 bytes) ROOT CYCLE: <ComGoogleCommonCollectLinkedListMultimap_Node 0x600001a075c0> [64]
  (64 bytes) next_ --> ROOT CYCLE: <ComGoogleCommonCollectLinkedListMultimap_Node 0x600001a07600> [64]
    previous_ --> CYCLE BACK TO <ComGoogleCommonCollectLinkedListMultimap_Node 0x600001a075c0> [64]
```

RELNOTES=n/a
PiperOrigin-RevId: 759770348

Author: java-team-github-bot

android/guava/src/com/google/common/collect/LinkedListMultimap.java

@@ -25,6 +25,7 @@
 import com.google.common.annotations.GwtIncompatible;
 import com.google.common.annotations.J2ktIncompatible;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
+import com.google.j2objc.annotations.Weak;
 import com.google.j2objc.annotations.WeakOuter;
 import java.io.IOException;
 import java.io.ObjectInputStream;
@@ -109,9 +110,9 @@ static final class Node<K extends @Nullable Object, V extends @Nullable Object>
     @ParametricNullness final K key;
     @ParametricNullness V value;
     @Nullable Node<K, V> next; // the next node (with any key)
-    @Nullable Node<K, V> previous; // the previous node (with any key)
+    @Weak @Nullable Node<K, V> previous; // the previous node (with any key)
     @Nullable Node<K, V> nextSibling; // the next node with the same key
-    @Nullable Node<K, V> previousSibling; // the previous node with the same key
+    @Weak @Nullable Node<K, V> previousSibling; // the previous node with the same key
 
     Node(@ParametricNullness K key, @ParametricNullness V value) {
       this.key = key;

guava/src/com/google/common/collect/LinkedListMultimap.java

@@ -26,6 +26,7 @@
 import com.google.common.annotations.GwtIncompatible;
 import com.google.common.annotations.J2ktIncompatible;
 import com.google.errorprone.annotations.CanIgnoreReturnValue;
+import com.google.j2objc.annotations.Weak;
 import com.google.j2objc.annotations.WeakOuter;
 import java.io.IOException;
 import java.io.ObjectInputStream;
@@ -112,9 +113,9 @@ static final class Node<K extends @Nullable Object, V extends @Nullable Object>
     @ParametricNullness final K key;
     @ParametricNullness V value;
     @Nullable Node<K, V> next; // the next node (with any key)
-    @Nullable Node<K, V> previous; // the previous node (with any key)
+    @Weak @Nullable Node<K, V> previous; // the previous node (with any key)
     @Nullable Node<K, V> nextSibling; // the next node with the same key
-    @Nullable Node<K, V> previousSibling; // the previous node with the same key
+    @Weak @Nullable Node<K, V> previousSibling; // the previous node with the same key
 
     Node(@ParametricNullness K key, @ParametricNullness V value) {
       this.key = key;