Remove extraneous doc id method (elastic#126570)

Removes docId. We can use _getDocId instead of docId instead. They are identical.

Author: jdconrad

server/src/main/java/org/elasticsearch/common/lucene/search/function/ScriptScoreFunction.java

@@ -64,7 +64,7 @@ public LeafScoreFunction getLeafScoreFunction(LeafReaderContext ctx) throws IOEx
 
         if (script.needs_termStats()) {
             assert termStatsFactory != null;
-            leafScript._setTermStats(termStatsFactory.apply(ctx, leafScript::docId));
+            leafScript._setTermStats(termStatsFactory.apply(ctx, leafScript::_getDocId));
         }
 
         return new LeafScoreFunction() {

server/src/main/java/org/elasticsearch/script/ScoreScript.java

@@ -116,11 +116,6 @@ public void setDocument(int docid) {
         this.docId = docid;
     }
 
-    /** Get the current document. */
-    public int docId() {
-        return docId;
-    }
-
     public void setScorer(Scorable scorer) {
         this.scoreSupplier = () -> {
             try {