remove redundant ctx.Err return in responseAction
remove redundant ctx.Err return in responseAction

I seem to remember it was useful when first writing this RunResponse
refactor, but evidently it's pointless right now. Fifty 'go test' runs
passed with no failures after this change.

Thanks to @Oiyoo for spotting this.

chromedp/chromedp,knq/chromedp,chromedp/chromedp,chromedp/chromedp,knq/chromedp,knq/chromedp