Fix pattern for humidity channels. Percent sign must be escaped.

[bdudelsack]

Not escaped percend sign in a channel pattern is causing a javascript error

angular.min.js:117 SyntaxError: [sprintf] unexpected placeholder
    at Function.b.parse (sprintf.min.js:3)
    at b (sprintf.min.js:3)
    at Object.getItemStateText (utility.js:1)
    at controllers.min.js:1
    at m.$eval (angular.min.js:145)
    at m.$apply (angular.min.js:145)
    at i (controllers.min.js:1)
    at controllers.min.js:1
    at Array.forEach (<anonymous>)
    at controllers.min.js:1

[HentschelT]

Thanks!