Update coroutines-guide.md (Kotlin#3600)

minor edits

Author: Julia-Alexandrova

docs/topics/coroutines-guide.md

@@ -1,15 +1,15 @@
 [//]: # (title: Coroutines guide)
 
-Kotlin, as a language, provides only minimal low-level APIs in its standard library to enable various other 
+Kotlin provides only minimal low-level APIs in its standard library to enable other 
 libraries to utilize coroutines. Unlike many other languages with similar capabilities, `async` and `await`
 are not keywords in Kotlin and are not even part of its standard library. Moreover, Kotlin's concept
 of _suspending function_ provides a safer and less error-prone abstraction for asynchronous 
 operations than futures and promises.  
 
 `kotlinx.coroutines` is a rich library for coroutines developed by JetBrains. It contains a number of high-level 
-coroutine-enabled primitives that this guide covers, including `launch`, `async` and others. 
+coroutine-enabled primitives that this guide covers, including `launch`, `async`, and others. 
 
-This is a guide on core features of `kotlinx.coroutines` with a series of examples, divided up into different topics.
+This is a guide about the core features of `kotlinx.coroutines` with a series of examples, divided up into different topics.
 
 In order to use coroutines as well as follow the examples in this guide, you need to add a dependency on the `kotlinx-coroutines-core` module as explained 
 [in the project README](https://github.com/Kotlin/kotlinx.coroutines/blob/master/README.md#using-in-your-projects).