Fix broken yarn.lock (elastic#17001)

yarn.lock

@@ -253,6 +253,12 @@ agent-base@2:
     extend "~3.0.0"
     semver "~5.0.1"
 
+agent-base@^4.1.0:
+  version "4.2.0"
+  resolved "https://registry.yarnpkg.com/agent-base/-/agent-base-4.2.0.tgz#9838b5c3392b962bad031e6a4c5e1024abec45ce"
+  dependencies:
+    es6-promisify "^5.0.0"
+
 agentkeepalive@^2.2.0:
   version "2.2.0"
   resolved "https://registry.yarnpkg.com/agentkeepalive/-/agentkeepalive-2.2.0.tgz#c5d1bd4b129008f1163f236f86e5faea2026e2ef"
@@ -5805,6 +5811,13 @@ https-browserify@^1.0.0:
   version "1.0.0"
   resolved "https://registry.yarnpkg.com/https-browserify/-/https-browserify-1.0.0.tgz#ec06c10e0a34c0f2faf199f7fd7fc78fffd03c73"
 
+[email protected]:
+  version "2.1.1"
+  resolved "https://registry.yarnpkg.com/https-proxy-agent/-/https-proxy-agent-2.1.1.tgz#a7ce4382a1ba8266ee848578778122d491260fd9"
+  dependencies:
+    agent-base "^4.1.0"
+    debug "^3.1.0"
+
 humanize-string@^1.0.0:
   version "1.0.1"
   resolved "https://registry.yarnpkg.com/humanize-string/-/humanize-string-1.0.1.tgz#fce2d6c545efc25dea1f23235182c98da0180b42"