Update TypeScript dependency to 3.9 (#1157)

* Update TypeScript dependency to 3.9

Fixes #1155

* Update test goldens

Author: rrdelaney

package.json

@@ -29,7 +29,7 @@
     "source-map-support": "^0.5.6",
     "tslib": "1.11",
     "tslint": "5.11.0",
-    "typescript": "3.8.2"
+    "typescript": "3.9"
   },
   "scripts": {
     "build": "bazel build //:npm_package",

test_files/cast_extends/cast_extends.js

@@ -1,5 +1,5 @@
-// test_files/cast_extends/cast_extends.ts(16,1): warning TS0: unhandled type flags: IncludesNonWideningType
-// test_files/cast_extends/cast_extends.ts(22,10): warning TS0: unhandled type flags: IncludesNonWideningType
+// test_files/cast_extends/cast_extends.ts(16,1): warning TS0: unhandled type flags: Intersection
+// test_files/cast_extends/cast_extends.ts(22,10): warning TS0: unhandled type flags: Intersection
 /**
  *
  * @fileoverview Reproduces an issue where tsickle would emit a cast for the "extends" claus, and

test_files/mixin/dtsdiagnostics.txt

@@ -1,2 +1,2 @@
-test_files/mixin/mixin.d.ts(1,1): warning TS0: unhandled type flags: IncludesNonWideningType
+test_files/mixin/mixin.d.ts(1,1): warning TS0: unhandled type flags: Intersection
 test_files/mixin/mixin.d.ts(12,31): warning TS0: dropped extends of non-symbol supertype: MyMixin(HTMLElement)

yarn.lock

@@ -1189,10 +1189,10 @@ tsutils@^2.27.2:
   dependencies:
     tslib "^1.8.1"
 
-typescript@3.8.2:
-  version "3.8.2"
-  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.8.2.tgz#91d6868aaead7da74f493c553aeff76c0c0b1d5a"
-  integrity sha512-EgOVgL/4xfVrCMbhYKUQTdF37SQn4Iw73H5BgCrF1Abdun7Kwy/QZsE/ssAy0y4LxBbvua3PIbFsbRczWWnDdQ==
+typescript@3.9:
+  version "3.9.5"
+  resolved "https://registry.yarnpkg.com/typescript/-/typescript-3.9.5.tgz#586f0dba300cde8be52dd1ac4f7e1009c1b13f36"
+  integrity sha512-hSAifV3k+i6lEoCJ2k6R2Z/rp/H3+8sdmcn5NrS3/3kE7+RyZXm9aqvxWqjEXHAd8b0pShatpcdMTvEdvAJltQ==
 
 uglify-js@^3.1.4:
   version "3.6.0"