Update stale documentation in overview.md

nextflow-io#4812 updated the syntax of the workflow in the example script to no longer use the `|` operator, but the accompanying description didn't change. This commit edits the description to bring it in line with the change in the workflow syntax.

Signed-off-by: greenberga <38597857+greenberga@users.noreply.github.com>

docs/overview.md

@@ -59,7 +59,7 @@ workflow {
 }
 ```
 
-The above example defines two processes. Their execution order is not determined by the fact that the `blastSearch` process comes before `extractTopHits` in the script (it could also be written the other way around). Instead, the pipe operator (`|`) in the workflow between `blastSearch` and `extractTopHits` forwards the outputs from one process to the inputs of the following one.
+The above example defines two processes. Their execution order is not determined by the fact that the `blastSearch` process comes before `extractTopHits` in the script (it could also be written the other way around). Instead, execution order is determined by their sequence in the _workflow_. In that block, `blastSearch` comes first, so it will execute first. `extractTopHits` executes after, and uses the output from `blastSearch`.
 
 When the workflow is started, it will create two processes and one channel (`query_ch`) and it will link all of them. Both processes will be started at the same time and they will listen to their respective input channels. Whenever `blastSearch` emits a value, `extractTopHits` will receive it (i.e. `extractTopHits` consumes the channel in a *reactive* way).