Fix incorrect “let’s” usages and restore “lets”

codespell-ignore-words.txt

@@ -3,4 +3,5 @@ assertIn
 IAM
 endcode
 deque
-thead
+thead
+lets

docs/api-guide/authentication.md

@@ -416,7 +416,7 @@ JSON Web Token is a fairly new standard which can be used for token-based authen
 
 ## Hawk HTTP Authentication
 
-The [HawkREST][hawkrest] library builds on the [Mohawk][mohawk] library to let you work with [Hawk][hawk] signed requests and responses in your API. [Hawk][hawk] let's two parties securely communicate with each other using messages signed by a shared key. It is based on [HTTP MAC access authentication][mac] (which was based on parts of [OAuth 1.0][oauth-1.0a]).
+The [HawkREST][hawkrest] library builds on the [Mohawk][mohawk] library to let you work with [Hawk][hawk] signed requests and responses in your API. [Hawk][hawk] lets two parties securely communicate with each other using messages signed by a shared key. It is based on [HTTP MAC access authentication][mac] (which was based on parts of [OAuth 1.0][oauth-1.0a]).
 
 ## HTTP Signature Authentication
 

docs/api-guide/serializers.md

@@ -430,7 +430,7 @@ The context dictionary can be used within any serializer field logic, such as a
 
 Often you'll want serializer classes that map closely to Django model definitions.
 
-The `ModelSerializer` class provides a shortcut that let's you automatically create a `Serializer` class with fields that correspond to the Model fields.
+The `ModelSerializer` class provides a shortcut that lets you automatically create a `Serializer` class with fields that correspond to the Model fields.
 
 **The `ModelSerializer` class is the same as a regular `Serializer` class, except that**: