Remove unused feature test_low_transition_point

Author: cuviper

.github/workflows/ci.yml

@@ -30,8 +30,6 @@ jobs:
             features:
           - rust: nightly
             bench: test build benchmarks
-          - rust: nightly
-            features: test_low_transition_point
 
     steps:
       - uses: actions/checkout@v2

Cargo.toml

@@ -46,7 +46,6 @@ serde-1 = ["serde"]
 std = []
 
 # for testing only, of course
-test_low_transition_point = []
 test_debug = []
 
 [profile.bench]