Remove 'First' section

Previously, there was a step missing instructing new users to create an
`out` directory before building. While it may have been obvious to those
that previously worked in the project, it should have existed. Now, in
upstream, the `Makefile` has been updated to perform this step
automatically, removing the need for this step to exist on the
end-user's side directly.

README.md

@@ -264,16 +264,6 @@ For further reading see the [Bootstrappable Builds](https://bootstrappable.org/)
 	
 * Gnu Make
 
-### First
-
-#### Create untracked build output directory
-
-From the `stagex` repository root:
-
-```shell
-mkdir out
-```
-
 ### Examples
 
 #### Reproduce entire tree