Fix typos in Mix.Phoenix.Schema docs (#5914)

lib/mix/phoenix/schema.ex

@@ -208,7 +208,7 @@ defmodule Mix.Phoenix.Schema do
   end
 
   @doc """
-  Converts the given value to map format when it is a date, time, datetime or naive_datetime.
+  Converts the given value to map format when it's a date, time, datetime or naive_datetime.
 
   Since `form.html.heex` generated by the live generator uses selects for dates and/or
   times, fixtures must use map format for those fields in order to submit the live form.
@@ -228,7 +228,7 @@ defmodule Mix.Phoenix.Schema do
   def live_form_value(value), do: value
 
   @doc """
-  Build an invalid value for `@invalid_attrs` which is nil by default.
+  Builds an invalid value for `@invalid_attrs` which is nil by default.
 
   * In case the value is a list, this will return an empty array.
   * In case the value is date, datetime, naive_datetime or time, this will return an invalid date.
@@ -260,7 +260,7 @@ defmodule Mix.Phoenix.Schema do
   end
 
   @doc """
-  Return the required fields in the schema. Anything not in the `optionals` list
+  Returns the required fields in the schema. Anything not in the `optionals` list
   is considered required.
   """
   def required_fields(schema) do