Remove underscore in copy_to heading (#10678)

Signed-off-by: kolchfa-aws <[email protected]>

Author: kolchfa-aws

_field-types/mapping-parameters/copy-to.md

@@ -1,14 +1,14 @@
 ---
 layout: default
-title: Copy_to
+title: Copy to
 parent: Mapping parameters
 
 nav_order: 20
 has_children: false
 has_toc: false
 ---
 
-# Copy_to
+# Copy to
 
 The `copy_to` parameter allows you to copy the values of multiple fields into a single field. This parameter can be useful if you often search across multiple fields because it allows you to search the group field instead.