pipeline: processors: filters: fix link to grep page

Signed-off-by: Nico Monchy <4321410+n-my@users.noreply.github.com>

Author: n-my

pipeline/processors/filters.md

@@ -4,7 +4,7 @@ Any Fluent Bit [filter](../filters/README.md) can be used as a processor.
 
 ## Grep example
 
-In this example, the [Grep](../filters/grep) filter is used as an output processor that sends log records only if they match a specified regular expression.
+In this example, the [Grep](../filters/grep.md) filter is used as an output processor that sends log records only if they match a specified regular expression.
 
 {% code title="fluent-bit.yaml" %}
 ```yaml