[DOCS] Updating heading for consistency. (#47619)

docs/java-rest/high-level/graph/explore.asciidoc

@@ -1,6 +1,6 @@
 [role="xpack"]
 [[java-rest-high-x-pack-graph-explore]]
-=== X-Pack Graph explore API
+=== Graph explore API
 
 [[java-rest-high-x-pack-graph-explore-execution]]
 ==== Initial request