Increase lower bound tolerance of future deref timeout test (#1185)

Hi,

can you please review to increase the lower bounder tolerance for the
`future` `deref` test with a timeout period. It addresses #1184.

The samples for the CI test failures suggested that the failures had an
error of -4ms, so I've increased the lower boundary to 95ms from 100ms.
If this proves to be insufficient, I will further increase it to 90ms.

I've also corrected the labelling from `ms` to `s` (for seconds), the
unit `perf-counter` returns.

I have not included this in the CHANGELOG, since I think is not
required.

Co-authored-by: ikappaki <[email protected]>
Co-authored-by: Chris Rink <[email protected]>

Author: ikappaki

tests/basilisp/test_core_fns.lpy

@@ -1546,7 +1546,7 @@
           end (time/perf-counter)
           diff (- end start)]
       (is (= :timed-out ret))
-      (is (< 0.1 diff 0.5) (str "deref timeout is outside of [100ms, 500ms] range: " diff "ms")))))
+      (is (< 0.1 diff 0.5) (str "deref timeout is outside of [100ms, 500ms] range: " diff "s")))))
 
 ;;;;;;;;;;;;;
 ;; Futures ;;
@@ -1573,8 +1573,14 @@
           end (time/perf-counter)
           diff (- end start)]
       (is (= :timed-out ret))
-      (is (< 0.1 diff 0.5) (str "deref timeout outside of [100ms, 500ms] range: " diff "ms"
-                              " -- :pre " pre " :start " start " :end " end))
+      ;; The lower bound is set to 95ms instead of 100ms due to an
+      ;; unexplained discrepancy observed on GitHub CI, where `deref`
+      ;; returned a few milliseconds before the time-out period
+      ;; elapsed.
+      ;;
+      ;; https://github.com/basilisp-lang/basilisp/issues/1184
+      (is (< 0.095 diff 0.5) (str "deref timeout outside of [95ms, 500ms] range: " diff "s"
+                                  " -- :pre " pre " :start " start " :end " end))
       (is (= false (future-cancelled? fut)))
       (is (= false (future-done? fut)))
       ;; can't always cancel a sleep-ed Future