[DOCS] Fixed typos (_op => op) in Painless context docs (#50301)

docs/painless/painless-contexts/painless-reindex-context.asciidoc

@@ -10,7 +10,7 @@ reindexed into a target index.
 `params` (`Map`, read-only)::
         User-defined parameters passed in as part of the query.
 
-`ctx['_op']` (`String`)::
+`ctx['op']` (`String`)::
         The name of the operation.
 
 {ref}/mapping-routing-field.html[`ctx['_routing']`] (`String`)::
@@ -34,7 +34,7 @@ reindexed into a target index.
 
 *Side Effects*
 
-`ctx['_op']`::
+`ctx['op']`::
         Use the default of `index` to update a document. Set to `none` to
         specify no operation or `delete` to delete the current document from
         the index.
@@ -65,4 +65,4 @@ reindexed into a target index.
 
 *API*
 
-The standard <<painless-api-reference-shared, Painless API>> is available.
+The standard <<painless-api-reference-shared, Painless API>> is available.

docs/painless/painless-contexts/painless-update-by-query-context.asciidoc

@@ -11,7 +11,7 @@ result of query.
 `params` (`Map`, read-only)::
         User-defined parameters passed in as part of the query.
 
-`ctx['_op']` (`String`)::
+`ctx['op']` (`String`)::
         The name of the operation.
 
 {ref}/mapping-routing-field.html[`ctx['_routing']`] (`String`, read-only)::
@@ -35,7 +35,7 @@ result of query.
 
 *Side Effects*
 
-`ctx['_op']`::
+`ctx['op']`::
         Use the default of `index` to update a document. Set to `none` to
         specify no operation or `delete` to delete the current document from
         the index.
@@ -91,4 +91,4 @@ POST /seats/_update_by_query
     }
 }
 --------------------------------------------------
-// TEST[setup:seats]
+// TEST[setup:seats]

docs/painless/painless-contexts/painless-update-context.asciidoc

@@ -9,7 +9,7 @@ add, modify, or delete fields within a single document.
 `params` (`Map`, read-only)::
         User-defined parameters passed in as part of the query.
 
-`ctx['_op']` (`String`)::
+`ctx['op']` (`String`)::
         The name of the operation.
 
 {ref}/mapping-routing-field.html[`ctx['_routing']`] (`String`, read-only)::
@@ -36,7 +36,7 @@ add, modify, or delete fields within a single document.
 
 *Side Effects*
 
-`ctx['_op']`::
+`ctx['op']`::
         Use the default of `index` to update a document. Set to `none` to
         specify no operation or `delete` to delete the current document from
         the index.
@@ -75,4 +75,4 @@ POST /seats/_update/3
     }
 }
 --------------------------------------------------
-// TEST[setup:seats]
+// TEST[setup:seats]