docs: [6598098782] add FILL mode restrictions for time-series functions in INTERVAL queries

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: Simon9997

docs/en/14-reference/03-taos-sql/20-select.md

@@ -371,6 +371,7 @@ The differences between NULL, NULL_F, VALUE, VALUE_F filling modes for different
 
 1. When using the FILL statement, a large amount of fill output may be generated, so be sure to specify the query time range. For each query, the system can return up to 10 million results with interpolation.
 2. FILL has continuity, if only the first value in a column is not NULL, then fill(prev) will fill all subsequent rows with that value.
+3. When using time-series specific functions (such as CSUM, DIFF, DERIVATIVE, MAVG, STATECOUNT, STATEDURATION, IRATE, TWA, LAG, LEAD, FILL_FORWARD) with INTERVAL queries, only FILL(NONE), FILL(NULL), FILL(NULL_F), FILL(VALUE), and FILL(VALUE_F) are supported. FILL(PREV), FILL(NEXT), FILL(LINEAR), and FILL(NEAR) are not supported with these functions.
 
 :::
 

docs/zh/14-reference/03-taos-sql/20-select.md

@@ -373,6 +373,7 @@ NULL、NULL_F、VALUE、VALUE_F 这几种填充模式针对不同场景区别如
 
 1. 使用 FILL 语句的时候可能生成大量的填充输出，务必指定查询的时间区间。针对每次查询，系统可返回不超过 1 千万条具有插值的结果。
 2. FILL 具有连续性，例如一列数据中仅第一条不为 NULL，则 FILL(PREV) 会为后续所有行填充该值。
+3. 当时序函数（如 CSUM、DIFF、DERIVATIVE、MAVG、STATECOUNT、STATEDURATION、IRATE、TWA、LAG、LEAD、FILL_FORWARD）与 INTERVAL 查询一起使用时，仅支持 FILL(NONE)、FILL(NULL)、FILL(NULL_F)、FILL(VALUE) 和 FILL(VALUE_F)。不支持 FILL(PREV)、FILL(NEXT)、FILL(LINEAR) 和 FILL(NEAR)。
 
 :::