Rename generated docs for (renamed) BUCKET func (#107299)

This checks in the generated-by-test doc files for newly renamed BUCKET
function.

docs/reference/esql/functions/kibana/definition/auto_bucket.json → docs/reference/esql/functions/kibana/definition/bucket.json

@@ -1,7 +1,7 @@
 {
   "comment" : "This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.",
   "type" : "eval",
-  "name" : "auto_bucket",
+  "name" : "bucket",
   "description" : "Creates human-friendly buckets and returns a datetime value\nfor each row that corresponds to the resulting bucket the row falls into.",
   "signatures" : [
     {

docs/reference/esql/functions/kibana/docs/auto_bucket.md → docs/reference/esql/functions/kibana/docs/bucket.md

@@ -2,7 +2,7 @@
 This is generated by ESQL's AbstractFunctionTestCase. Do no edit it. See ../README.md for how to regenerate it.
 -->
 
-### AUTO_BUCKET
+### BUCKET
 Creates human-friendly buckets and returns a datetime value
 for each row that corresponds to the resulting bucket the row falls into.