ESQL: Fix typo in docs readme

s/and/are/

docs/reference/esql/functions/README.md

@@ -1,4 +1,4 @@
-The files in these subdirectories and generated by ESQL's test suite:
+The files in these subdirectories are generated by ESQL's test suite:
 * `description` - description of each function scraped from `@FunctionInfo#description`
 * `examples` - examples of each function scraped from `@FunctionInfo#examples`
 * `parameters` - description of each function's parameters scraped from `@Param`