docs($resource): re-phrase warning message (has to --> would)

As discussed in #13462 (comment).

Author: gkalpak

src/ngResource/resource.js

@@ -582,8 +582,8 @@ angular.module('ngResource', ['ng']).
             if (action.timeout) {
               $log.debug('ngResource:\n' +
                          '  Only numeric values are allowed as `timeout`.\n' +
-                         '  Promises are not supported in $resource, because the same value has to ' +
-                         'be re-used for multiple requests. If you are looking for a way to cancel ' +
+                         '  Promises are not supported in $resource, because the same value would ' +
+                         'be used for multiple requests. If you are looking for a way to cancel ' +
                          'requests, you should use the `cancellable` option.');
               delete action.timeout;
             }

test/ngResource/resourceSpec.js

@@ -1421,8 +1421,8 @@ describe('cancelling requests', function() {
       expect(httpSpy.calls[0].args[0].timeout).toBeUndefined();
       expect($log.debug).toHaveBeenCalledOnceWith('ngResource:\n' +
           '  Only numeric values are allowed as `timeout`.\n' +
-          '  Promises are not supported in $resource, because the same value has to ' +
-          'be re-used for multiple requests. If you are looking for a way to cancel ' +
+          '  Promises are not supported in $resource, because the same value would ' +
+          'be used for multiple requests. If you are looking for a way to cancel ' +
           'requests, you should use the `cancellable` option.');
     })
   );