memo: Remove local program / client and point to new repo (#7535)

memo: Remove local programs and point to new repo

#### Problem

The memo program and clients now live at their own repo, but the code
still exists in the SPL repo.

#### Summary of changes

* Update documentation for the memo program's new home
* Remove program directory, update Rust dependencies to crates.io version
* Remove JS bindings
* Remove CI files

Author: joncinque

docs/src/memo.md

@@ -20,7 +20,7 @@ document are available at:
 ## Source
 
 The Memo Program's source is available on
-[GitHub](https://github.com/solana-labs/solana-program-library)
+[GitHub](https://github.com/solana-program/memo)
 
 ## Interface