Fix typo in markOutputAs to markOutputsAs

I think this should be plural?

Author: martinbonnin

docs/src/user-guide/plugins/topics/tasks.md

@@ -214,7 +214,7 @@ It has two properties: `modifier: string` and `isTest: boolean`.
 The `modifier` string has the same semantics as the suffix one can put after the `@` in the `module.yaml` configuration or
 in the names of `src` directories. For example, having:
 ```yaml
-markOutputAs:
+markOutputsAs:
   - path: ${action.generatedSourceDir}
     kind: kotlin-sources
     fragment:
@@ -349,4 +349,4 @@ We are working on providing a proper UX for calling plugin tasks.
 
 To see more practical examples of how to write tasks,
 you are welcome to check out the [quick start guide](../quick-start.md) and our
-plugin samples in the `build-sources` directory of the Amper project.
+plugin samples in the `build-sources` directory of the Amper project.