Revert introduction of [workspace.dependencies].

This was done in #145740 and #145947. It is causing problems for people
using r-a on anything that uses the rustc-dev rustup package, e.g. Miri,
clippy.

This repository has lots of submodules and subtrees and various
different projects are carved out of pieces of it. It seems like
`[workspace.dependencies]` will just be more trouble than it's worth.

compiler/rustc_next_trait_solver/Cargo.toml

@@ -5,13 +5,13 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-derive-where.workspace = true
+derive-where = "1.2.7"
 rustc_data_structures = { path = "../rustc_data_structures", optional = true }
 rustc_index = { path = "../rustc_index", default-features = false }
 rustc_macros = { path = "../rustc_macros", optional = true }
 rustc_type_ir = { path = "../rustc_type_ir", default-features = false }
 rustc_type_ir_macros = { path = "../rustc_type_ir_macros" }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end
 
 [features]