fix(form): length is deprececated and doubled since 2.0.6

The length rule is deprecated since SUI 2.0.6, instead minLength, maxLength and exactLength were introduced back then.
Even the docs do not use it in any examples

src/definitions/behaviors/form.js

@@ -1586,7 +1586,6 @@ $.fn.form.settings = {
     doesntContain        : '{name} cannot contain  "{ruleValue}"',
     doesntContainExactly : '{name} cannot contain exactly "{ruleValue}"',
     minLength            : '{name} must be at least {ruleValue} characters',
-    length               : '{name} must be at least {ruleValue} characters',
     exactLength          : '{name} must be exactly {ruleValue} characters',
     maxLength            : '{name} cannot be longer than {ruleValue} characters',
     match                : '{name} must match {ruleValue} field',
@@ -1866,14 +1865,6 @@ $.fn.form.settings = {
       ;
     },
 
-    // see rls notes for 2.0.6 (this is a duplicate of minLength)
-    length: function(value, requiredLength) {
-      return (value !== undefined)
-        ? (value.length >= requiredLength)
-        : false
-      ;
-    },
-
     // is exactly length
     exactLength: function(value, requiredLength) {
       return (value !== undefined)