Simplify dictionary update

Sourcery refactoring id: simplify-dictionary-update

Description:

Add single value to dictionary directly rather than using update()

Before:

def foo(d: dict) -> None:
    d.update({"request": HttpRequest()})
    frobnicate(d)

After:

def foo(d: dict) -> None:
    d["request"] = HttpRequest()
    frobnicate(d)

Explanation:

When we are just adding one entry to a dictionary it is simpler to do it directly rather than via the update() method. This also eliminates the overhead of constructing another dictionary and calling a method, so should slightly improve performance.