dev-lang/rust: don't generate extra lockfiles

This causes problems with stale crate induced breakage that upstream
rust doesn't appear to be affected by. Notably this downgraded crates to
older versions than what were available at src_prepare time.

Removing this got me around this issue and I didn't encounter workspaces
needing this.

In this instance, we hit an issue w/ icu_properties being pinned when
upstream CI doesn't seem to be hitting that:
```
	Locking 510 packages to latest compatible versions
	...
	Adding icu_properties v2.0.1 (available: v2.1.1)
```

That said, we seem to pass locked-deps in our bootstrap args, as upstream
CI does at 503dce33e2/src/ci/run.sh (L66).

[sam: Include an example.]

Bug: https://github.com/unicode-org/icu4x/issues/7190
Signed-off-by: Alfred Wingate <parona@protonmail.com>
Signed-off-by: Sam James <sam@gentoo.org>

dev-lang/rust/rust-9999.ebuild

@@ -324,11 +324,6 @@ src_unpack() {
 }
 
 src_prepare() {
-	if [[ ${PV} = *9999* ]]; then
-		# We need to update / generate lockfiles for the workspace
-		${CARGO} generate-lockfile --offline || die "Failed to generate lockfiles"
-	fi
-
 	# Commit patches to the appropriate branch in proj/rust-patches.git
 	# then cut a new tag / tarball. Don't add patches to ${FILESDIR}
 	PATCHES=(