[DOCS][ESQL] Flip preview booleans, to GA search functions

Author: leemthompo

docs/reference/query-languages/esql/kibana/definition/functions/kql.json

@@ -35,7 +35,6 @@ public class Kql extends FullTextFunction {
 
     @FunctionInfo(
         returnType = "boolean",
-        preview = true,
         description = "Performs a KQL query. Returns true if the provided KQL query string matches the row.",
         examples = { @Example(file = "kql-function", tag = "kql-with-field") }
     )

docs/reference/query-languages/esql/kibana/definition/functions/match.json

@@ -135,7 +135,6 @@ public class Match extends FullTextFunction implements OptionalArgument, PostAna
 
     @FunctionInfo(
         returnType = "boolean",
-        preview = true,
         description = """
             Use `MATCH` to perform a <<query-dsl-match-query,match query>> on the specified field.
             Using `MATCH` is equivalent to using the `match` query in the Elasticsearch Query DSL.

docs/reference/query-languages/esql/kibana/definition/functions/match_phrase.json

@@ -28,7 +28,6 @@ public class MatchOperator extends Match {
     @FunctionInfo(
         returnType = "boolean",
         operator = ":",
-        preview = true,
         description = """
             Use the match operator (`:`) to perform a <<query-dsl-match-query,match query>> on the specified field.
             Using `:` is equivalent to using the `match` query in the Elasticsearch Query DSL.

docs/reference/query-languages/esql/kibana/definition/functions/qstr.json

@@ -92,7 +92,6 @@ public class MatchPhrase extends FullTextFunction implements OptionalArgument, P
 
     @FunctionInfo(
         returnType = "boolean",
-        preview = true,
         description = """
             Use `MATCH_PHRASE` to perform a [`match_phrase`](/reference/query-languages/query-dsl/query-dsl-match-query-phrase.md) on the
             specified field.

docs/reference/query-languages/esql/kibana/definition/operators/match_operator.json

@@ -104,7 +104,6 @@ public class QueryString extends FullTextFunction implements OptionalArgument {
 
     @FunctionInfo(
         returnType = "boolean",
-        preview = true,
         description = "Performs a <<query-dsl-query-string-query,query string query>>. "
             + "Returns true if the provided query string matches the row.",
         examples = {