fix(deps): Limit semantic-release peer-dep to <20

There is a breaking ESM change in `semantic-release` 20.

Also removes unused `env-ci` dependency.

Author: pmowrer

package.json

@@ -16,11 +16,10 @@
   "bin": "./bin/semantic-release-github-pr.js",
   "license": "MIT",
   "peerDependencies": {
-    "semantic-release": ">=16.0.0"
+    "semantic-release": ">=16.0.0 < 20"
   },
   "dependencies": {
     "debug": "^4.1.1",
-    "env-ci": "^5.0.1",
     "execa": "^4.0.0",
     "github": "^13.0.0",
     "parse-github-url": "^1.0.2",
@@ -33,7 +32,7 @@
     "jest": "^25.1.0",
     "lint-staged": "^10.0.3",
     "prettier": "^1.19.1",
-    "semantic-release": "^17.0.0"
+    "semantic-release": "^19"
   },
   "husky": {
     "hooks": {