Removed support for custom promise libraries

All supported platforms now provide promises, so there's no longer a need
for Jasmine to be able to create them via a user-provided library. Jasmine
can still consume non-native promises but will always use the built-in
Promise object to create promises.

[#179078103]

src/core/SpyStrategy.js

@@ -27,24 +27,6 @@ getJasmineRequireObj().SpyStrategy = function(j$) {
       }
     }
 
-    var getPromise =
-      typeof options.getPromise === 'function'
-        ? options.getPromise
-        : function() {};
-
-    var requirePromise = function(name) {
-      var Promise = getPromise();
-
-      if (!Promise) {
-        throw new Error(
-          name +
-            ' requires global Promise, or `Promise` configured with `jasmine.getEnv().configure()`'
-        );
-      }
-
-      return Promise;
-    };
-
     /**
      * Tell the spy to return a promise resolving to the specified value when invoked.
      * @name SpyStrategy#resolveTo
@@ -53,7 +35,6 @@ getJasmineRequireObj().SpyStrategy = function(j$) {
      * @param {*} value The value to return.
      */
     this.resolveTo = function(value) {
-      var Promise = requirePromise('resolveTo');
       self.plan = function() {
         return Promise.resolve(value);
       };
@@ -68,8 +49,6 @@ getJasmineRequireObj().SpyStrategy = function(j$) {
      * @param {*} value The value to return.
      */
     this.rejectWith = function(value) {
-      var Promise = requirePromise('rejectWith');
-
       self.plan = function() {
         return Promise.reject(value);
       };