term2.rs: Add `dyn` to various Box<> types
term2.rs: Add `dyn` to various Box<> types

In order to prepare for when missing `dyn` is a warning or even
an error, add them in where we need them.  These were spotted by
the current nightly toolchain.

Signed-off-by: Daniel Silverstone <3cc17a76d780e0cd3d87bad586a1c53967be5625@digital-scurf.org>

inejge/rustup.rs,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,rust-lang/rustup,rust-lang/rustup,nodakai/rustup.rs,nodakai/rustup.rs,rust-lang/rustup,nodakai/rustup.rs,inejge/rustup.rs,inejge/rustup.rs,inejge/rustup.rs,inejge/rustup.rs,rust-lang/rustup