docs(uppercase, lowercase): undocument these artifacts

Closes #11387
Closes #13779

Author: thorn0

src/Angular.js

@@ -119,29 +119,9 @@ var REGEX_STRING_REGEXP = /^\/(.+)\/([a-z]*)$/;
 // This is used so that it's possible for internal tests to create mock ValidityStates.
 var VALIDITY_STATE_PROPERTY = 'validity';
 
-/**
- * @ngdoc function
- * @name angular.lowercase
- * @module ng
- * @kind function
- *
- * @description Converts the specified string to lowercase.
- * @param {string} string String to be converted to lowercase.
- * @returns {string} Lowercased string.
- */
-var lowercase = function(string) {return isString(string) ? string.toLowerCase() : string;};
 var hasOwnProperty = Object.prototype.hasOwnProperty;
 
-/**
- * @ngdoc function
- * @name angular.uppercase
- * @module ng
- * @kind function
- *
- * @description Converts the specified string to uppercase.
- * @param {string} string String to be converted to uppercase.
- * @returns {string} Uppercased string.
- */
+var lowercase = function(string) {return isString(string) ? string.toLowerCase() : string;};
 var uppercase = function(string) {return isString(string) ? string.toUpperCase() : string;};
 
 
@@ -161,7 +141,7 @@ var manualUppercase = function(s) {
 
 // String#toLowerCase and String#toUpperCase don't produce correct results in browsers with Turkish
 // locale, for this reason we need to detect this case and redefine lowercase/uppercase methods
-// with correct but slower alternatives.
+// with correct but slower alternatives. See https://github.com/angular/angular.js/issues/11387
 if ('i' !== 'I'.toLowerCase()) {
   lowercase = manualLowercase;
   uppercase = manualUppercase;