Removed redundant borrow

As described here https://rust-lang.github.io/rust-clippy/master/#needless_borrow.
rust-clippy is complaining that the related borrows are unnecessary.

src/cargo/ops/cargo_install.rs

@@ -287,7 +287,7 @@ fn install_one(
  } else {
  let tracker = InstallTracker::load(config, root)?;
  let (freshness, _duplicates) =
- tracker.check_upgrade(&dst, pkg, force, opts, &target, &rustc.verbose_version)?;
+ tracker.check_upgrade(&dst, pkg, force, opts, target, &rustc.verbose_version)?;
  if freshness == Freshness::Fresh {
  let msg = format!(
  "package `{}` is already installed, use --force to override",
@@ -341,7 +341,7 @@ fn install_one(
  } else {
  let tracker = InstallTracker::load(config, root)?;
  let (_freshness, duplicates) =
- tracker.check_upgrade(&dst, pkg, force, opts, &target, &rustc.verbose_version)?;
+ tracker.check_upgrade(&dst, pkg, force, opts, target, &rustc.verbose_version)?;
  (Some(tracker), duplicates)
  };
 
@@ -408,7 +408,7 @@ fn install_one(
  &successful_bins,
  vers.map(|s| s.to_string()),
  opts,
- &target,
+ target,
  &rustc.verbose_version,
  );