docs($provide): clarify value and constant injectability

Closes angular#14168

Author: Narretz

src/auto/injector.js

@@ -544,14 +544,13 @@ function annotate(fn, strictDi, name) {
  * @description
  *
  * Register a **value service** with the {@link auto.$injector $injector}, such as a string, a
- * number, an array, an object or a function.  This is short for registering a service where its
+ * number, an array, an object or a function. This is short for registering a service where its
  * provider's `$get` property is a factory function that takes no arguments and returns the **value
- * service**.
+ * service**. That also means it is not possible to inject other services into a value service.
  *
  * Value services are similar to constant services, except that they cannot be injected into a
  * module configuration function (see {@link angular.Module#config}) but they can be overridden by
- * an Angular
- * {@link auto.$provide#decorator decorator}.
+ * an Angular {@link auto.$provide#decorator decorator}.
  *
  * @param {string} name The name of the instance.
  * @param {*} value The value.
@@ -576,8 +575,11 @@ function annotate(fn, strictDi, name) {
  * @name $provide#constant
  * @description
  *
- * Register a **constant service**, such as a string, a number, an array, an object or a function,
- * with the {@link auto.$injector $injector}. Unlike {@link auto.$provide#value value} it can be
+ * Register a **constant service** with the {@link auto.$injector $injector}, such as a string,
+ * a number, an array, an object or a function. Like the {@link auto.$provide#value value}, it is not
+ * possible to inject other services into a constant.
+ *
+ * But unlike {@link auto.$provide#value value}, a constant can be
  * injected into a module configuration function (see {@link angular.Module#config}) and it cannot
  * be overridden by an Angular {@link auto.$provide#decorator decorator}.
  *