Fix several minor typos (#1603)

readthedocs/basic/quick-start.rst

@@ -19,7 +19,7 @@ use these if possible.
         # Getting information about yourself
         me = await client.get_me()
 
-        # "me" is an User object. You can pretty-print
+        # "me" is a user object. You can pretty-print
         # any Telegram object with the "stringify" method:
         print(me.stringify())
 

readthedocs/concepts/entities.rst

@@ -289,7 +289,7 @@ applications"? Now do the same with the library. Use what applies:
 
     # (These examples assume you are inside an "async def")
     async with client:
-        # Does it have an username? Use it!
+        # Does it have a username? Use it!
         entity = await client.get_entity(username)
 
         # Do you have a conversation open with them? Get dialogs.

readthedocs/misc/changelog.rst

@@ -3806,7 +3806,7 @@ things with the ``InteractiveTelegramClient``:
 - **Download** any message's media (photos, documents or even contacts!).
 - **Receive message updates** as you talk (i.e., someone sent you a message).
 
-It actually is an usable-enough client for your day by day. You could
+It actually is a usable-enough client for your day by day. You could
 even add ``libnotify`` and pop, you're done! A great cli-client with
 desktop notifications.
 

readthedocs/quick-references/client-reference.rst

@@ -9,7 +9,7 @@ you may need when using Telethon. They are sorted by relevance and are not in
 alphabetical order.
 
 You should use this page to learn about which methods are available, and
-if you need an usage example or further description of the arguments, be
+if you need a usage example or further description of the arguments, be
 sure to follow the links.
 
 .. contents::