test: remove unnecessary miri flags

src/relax.rs

@@ -246,16 +246,8 @@ impl RelaxImpl for YieldBackoff {
 type Uint = u32;
 
 /// The default max number of shifts the inner value of `Backoff` will produce.
-#[cfg(not(miri))]
 const DEFAULT_SHIFTS: Uint = 6;
 
-/// The default max number of shifts the inner value of `Backoff` will produce.
-///
-/// For testing purposes, lets make this super small, else Miri runs will take
-/// far more time without much benefit.
-#[cfg(miri)]
-const DEFAULT_SHIFTS: Uint = 1;
-
 /// Inner backoff counter that keeps track of the number of shifts applied.
 ///
 /// The maximum value the inner shift counter can take is defined by `MAX`.