docs: improve copy_history syntax docs (#3020)

Author: BohuTANG

docs/cn/sql-reference/00-sql-reference/31-system-tables/system-copy-history.md

@@ -8,8 +8,16 @@ import FunctionDescription from '@site/src/components/FunctionDescription';
 
 包含 COPY 历史的相关信息。
 
+## Syntax
+
+```sql
+SELECT * FROM copy_history('<table_name>');
+```
+
+- `table_name`: 表名。
+
 ```sql
-select * from copy_history('abc');
+select * from copy_history('my_table');
 
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docs/en/sql-reference/00-sql-reference/31-system-tables/system-copy-history.md

@@ -8,8 +8,16 @@ import FunctionDescription from '@site/src/components/FunctionDescription';
 
 Contains information about copy history.
 
+## Syntax
+
+```sql
+SELECT * FROM copy_history('<table_name>');
+```
+
+- `table_name`: The table name.
+
 ```sql
-select * from copy_history('abc');
+select * from copy_history('my_table');
 
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