Remove blankLine localized string

Using a nbsp is more correct and lets the screen reader handle how it wants

Fixes #2260

src/browser/LocalizableStrings.ts

@@ -3,6 +3,5 @@
  * @license MIT
  */
 
-export let blankLine = 'Blank line';
 export let promptLabel = 'Terminal input';
 export let tooMuchOutput = 'Too much output to announce, navigate to rows manually to read';