Update router.md (fluent#1633)

Fix small typo: matching tag prefix for routing with wildcard example

Signed-off-by: Poupapaa <[email protected]>
Signed-off-by: Tom <[email protected]>

Author: poupapaa

concepts/data-pipeline/router.md

@@ -76,7 +76,7 @@ example defines a common destination for both sources of data:
     Match  my_*
 ```
 
-The match rule is set to `my_*`, which matches any Tag starting with `my_*`.
+The match rule is set to `my_*`, which matches any Tag starting with `my_`.
 
 ## Routing with Regex