Remove trailing spaces before check for invalid rule

I use cut and paste a lot and all too often a trailing space is inserted without me seeing it, which happened while pasting in a schedule into a single job entry. I was actually going to submit a bug / support request because I was certain I had the correct syntax (cron is not new to me). Long story short, a trailing space was causing the invalid rule.

I propose the following simple patch to remove trailing whitespace before saving the variable in elysia_cron_settings_form_submit(), works for me.