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_mir_dataflow/Cargo.toml

@@ -5,7 +5,7 @@ edition = "2024"
 
 [dependencies]
 # tidy-alphabetical-start
-polonius-engine.workspace = true
+polonius-engine = "0.13.0"
 regex = "1"
 rustc_abi = { path = "../rustc_abi" }
 rustc_ast = { path = "../rustc_ast" }
@@ -18,5 +18,5 @@ rustc_macros = { path = "../rustc_macros" }
 rustc_middle = { path = "../rustc_middle" }
 rustc_span = { path = "../rustc_span" }
 smallvec = { version = "1.8.1", features = ["union", "may_dangle"] }
-tracing.workspace = true
+tracing = "0.1"
 # tidy-alphabetical-end