[Chore][OAS] Remove use of any in generator lib utility (#192440)

## Summary

Tiny change, using a cast to `Record` instead of relying on `any`.

(cherry picked from commit 9c18dfa)

packages/kbn-router-to-openapispec/src/oas_converter/kbn_config_schema/post_process_mutations/mutations/utils.ts

@@ -43,8 +43,8 @@ export const processDiscontinued = (schema: OpenAPIV3.SchemaObject): void => {
 };
 
 /** Just for type convenience */
-export const deleteField = (schema: Record<any, unknown>, field: string): void => {
-  delete schema[field];
+export const deleteField = (schema: object, field: string): void => {
+  delete (schema as Record<string, unknown>)[field];
 };
 
 export const isAnyType = (schema: OpenAPIV3.SchemaObject): boolean => {