chore(cli): extract misleading language in job manifest for rates (#1554)

<!-- Provide summary of changes -->
At some point, we decided not to accept simple duration strings like "1h30m" in favor of the "@every 1h30m" syntax. 

This PR rewords the comment in the manifest to clarify the required syntax. 
<!-- Issue number, if available. E.g. "Fixes #31", "Addresses #42, 77" -->

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Author: bvtujo

internal/pkg/manifest/testdata/scheduled-job-fully-specified.yml

@@ -18,7 +18,7 @@ cpu: 256
 memory: 512
 
 on:
-  # The scheduled trigger for your job. You can specify a cron schedule or keyword (@weekly) or a rate (2h, 1h30m, 15m)
+  # The scheduled trigger for your job. You can specify a Unix cron schedule or keyword (@weekly) or a rate (@every 1h30m)
   # AWS Schedule Expressions are also accepted: https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
   schedule: "0 */2 * * *"
 

internal/pkg/manifest/testdata/scheduled-job-no-retries.yml

@@ -18,7 +18,7 @@ cpu: 256
 memory: 512
 
 on:
-  # The scheduled trigger for your job. You can specify a cron schedule or keyword (@weekly) or a rate (2h, 1h30m, 15m)
+  # The scheduled trigger for your job. You can specify a Unix cron schedule or keyword (@weekly) or a rate (@every 1h30m)
   # AWS Schedule Expressions are also accepted: https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
   schedule: "@every 5h"
 

internal/pkg/manifest/testdata/scheduled-job-no-timeout-or-retries.yml

@@ -18,7 +18,7 @@ cpu: 256
 memory: 512
 
 on:
-  # The scheduled trigger for your job. You can specify a cron schedule or keyword (@weekly) or a rate (2h, 1h30m, 15m)
+  # The scheduled trigger for your job. You can specify a Unix cron schedule or keyword (@weekly) or a rate (@every 1h30m)
   # AWS Schedule Expressions are also accepted: https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
   schedule: "@weekly"
 

internal/pkg/manifest/testdata/scheduled-job-no-timeout.yml

@@ -18,7 +18,7 @@ cpu: 256
 memory: 512
 
 on:
-  # The scheduled trigger for your job. You can specify a cron schedule or keyword (@weekly) or a rate (2h, 1h30m, 15m)
+  # The scheduled trigger for your job. You can specify a Unix cron schedule or keyword (@weekly) or a rate (@every 1h30m)
   # AWS Schedule Expressions are also accepted: https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
   schedule: "@every 5h"
 

templates/workloads/jobs/scheduled-job/manifest.yml

@@ -24,7 +24,7 @@ cpu: {{.CPU}}
 memory: {{.Memory}}
 
 on:
-  # The scheduled trigger for your job. You can specify a cron schedule or keyword (@weekly) or a rate (2h, 1h30m, 15m)
+  # The scheduled trigger for your job. You can specify a Unix cron schedule or keyword (@weekly) or a rate (@every 1h30m)
   # AWS Schedule Expressions are also accepted: https://docs.aws.amazon.com/AmazonCloudWatch/latest/events/ScheduledEvents.html
   schedule: "{{.On.Schedule}}"