avm: Remove avm from workspaces

[tomlinton]

Move avm out of the workspace config to avoid the error below on cargo build in the root. It looks like when Cargo has a --git argument it looks in the whole repo for a package named avm so I don't believe we need to update the install command for avm in the book.

warning: output filename collision.
The bin target `anchor` in package `avm v0.22.0 (/Users/tom/Code/anchor/avm)` has the same output filename as the bin target `anchor` in package `anchor-cli v0.22.0 (/Users/tom/Code/anchor/cli)`.
Colliding filename is: /Users/tom/Code/anchor/target/debug/anchor.dSYM
The targets should have unique names.
Consider changing their names to be unique or compiling them separately.
This may become a hard error in the future; see <https://github.com/rust-lang/cargo/issues/6313>.

[paul-schaaf]

yup I can still download avm with the same command from your fork

[paul-schaaf]

thank you!