add missing feature gate on ConfigExt for no-features build

[HoKim98]

Motivation

Fixes #1548

Solution

In kube/src/lib.rs:L197,

Before

pub mod prelude {
    #[allow(unreachable_pub)] pub use crate::client::ConfigExt as _;
    ...
}

After

pub mod prelude {
    #[cfg(feature = "client")]
    #[allow(unreachable_pub)]
    pub use crate::client::ConfigExt as _;
    ...
}

[clux]

Thank you!

[HoKim98]

Re-committed to pass rust-fmt!

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 75.7%. Comparing base (5b3b73d) to head (29dfc10).

Additional details and impacted files

@@          Coverage Diff          @@
##            main   #1549   +/-   ##
=====================================
  Coverage   75.7%   75.7%           
=====================================
  Files         79      79           
  Lines       7252    7252           
=====================================
  Hits        5487    5487           
  Misses      1765    1765           

Files	Coverage Δ
kube/src/lib.rs	88.5% <ø> (ø)

[clux]

I'll do a patch release with this shortly.

EDIT: released in 0.93.1