Update Clojure Homebrew setup details

[practicalli-johnny]

Update development tool setup guide to use Clojure.org homebrew recipe
https://clojure.org/guides/getting_started

Background
Currently Homebrew will install OpenJDK 13, which is not a long term support (LTS) version of Java and will be depreciated as soon the next version is released.

Clojure is not tested on these transitory releases and is not guaranteed to work.

We should recommend avoiding Homebrew and installing openjdk manually.

Setting JAVA_HOME can help if you have an existing Java installation, but not all Java tooling will respect this environment variable or may be over-ridden by the path precedence.

See discussion
Homebrew/homebrew-core@715900b
And issue
Homebrew/homebrew-core#50536

[puredanger]

Note that there are no known issues with Java 13 and Clojure (or even Java 14), it's just not what is tested on our CI test matrix or officially recommended.

[practicalli-johnny]

We should update the development tools setup guide to recommend the Clojure.org homebrew recipe, as defined in:

https://clojure.org/guides/getting_started