Unify title for explain overview (pingcap#8095)

Author: Oreoxmt

blocklist-control-plan.md

@@ -146,7 +146,7 @@ To remove one or more expressions from the blocklist, perform the following step
 
 In the following example, the `<` and `>` operators are added to the blocklist, and then the `>` operator is removed from the blocklist.
 
-To judge whether the blocklist takes effect, observe the results of `EXPLAIN` (See [Optimize SQL statements using `EXPLAIN`](/explain-overview.md)).
+To judge whether the blocklist takes effect, observe the results of `EXPLAIN` (See [TiDB Query Execution Plan Overview](/explain-overview.md)).
 
 1. The predicates `a < 2` and `a > 2` in the `WHERE` clause of the following SQL statement can be pushed down to TiKV.
 

explain-overview.md

@@ -1,10 +1,10 @@
 ---
-title: EXPLAIN Overview
+title: TiDB Query Execution Plan Overview
 summary: Learn about the execution plan information returned by the `EXPLAIN` statement in TiDB.
 aliases: ['/docs/dev/query-execution-plan/','/docs/dev/reference/performance/understanding-the-query-execution-plan/','/docs/dev/index-merge/','/docs/dev/reference/performance/index-merge/','/tidb/dev/index-merge','/tidb/dev/query-execution-plan']
 ---
 
-# `EXPLAIN` Overview
+# TiDB Query Execution Plan Overview
 
 > **Note:**
 >