drop the maybe_uninit feature gate

ci/script.sh

@@ -11,7 +11,7 @@ main() {
         if [ $TRAVIS_RUST_VERSION = nightly ]; then
             export RUSTFLAGS="-Z sanitizer=thread"
             export RUST_TEST_THREADS=1
-            export TSAN_OPTIONS="suppressions=$(pwd)/blacklist.txt"
+            export TSAN_OPTIONS="suppressions=$(pwd)/suppressions.txt"
 
             cargo test --test tsan --target $TARGET
             cargo test --test tsan --target $TARGET --release

src/lib.rs

@@ -64,7 +64,6 @@
 #![deny(rust_2018_compatibility)]
 #![deny(rust_2018_idioms)]
 #![deny(warnings)]
-#![feature(maybe_uninit)]
 
 pub use binary_heap::BinaryHeap;
 pub use generic_array::typenum::consts;