deps: get rid of unstable feature

This was introduced as a temporary measure for dealing with the regex
crate's unstable feature, but it was never included in a release of
ripgrep. Thus, we remove it. The regex crate will now automatically enable
SIMD optimizations when available.

Cargo.toml

@@ -69,13 +69,13 @@ default-features = false
 features = ["suggestions", "color"]
 
 [features]
-avx-accel = ["bytecount/avx-accel", "regex/unstable"]
+avx-accel = [
+  "bytecount/avx-accel",
+]
 simd-accel = [
   "bytecount/simd-accel",
   "encoding_rs/simd-accel",
-  "regex/unstable",
 ]
-unstable = ["regex/unstable"]
 
 [profile.release]
 debug = true

appveyor.yml

@@ -50,7 +50,7 @@ test_script:
 
 before_deploy:
   # Generate artifacts for release
-  - cargo build --release --features unstable
+  - cargo build --release
   - mkdir staging
   - copy target\release\rg.exe staging
   - ps: copy target\release\build\ripgrep-*\out\_rg.ps1 staging

ci/before_deploy.sh

@@ -8,7 +8,7 @@ set -ex
 
 # Generate artifacts for release
 mk_artifacts() {
-    cargo build --target "$TARGET" --release --features unstable
+    cargo build --target "$TARGET" --release
 }
 
 mk_tarball() {