remove channel default from dist profile

Signed-off-by: onur-ozkan <work@onurozkan.dev>

Author: onur-ozkan

src/bootstrap/defaults/bootstrap.dist.toml

@@ -13,9 +13,6 @@ extended = true
 download-ci-llvm = false
 
 [rust]
-# We have several defaults in bootstrap that depend on whether the channel is `dev` (e.g. `omit-git-hash` and `download-ci-llvm`).
-# Make sure they don't get set when installing from source.
-channel = "nightly"
 # Never download a rustc, distributions must build a fresh compiler.
 download-rustc = false
 lld = true