fix(@schematics/angular): remove target and lib options for library tsconfig

The `target` option is set directly in ng-packagr binary and cannot be overridden, while the `lib` option is inherited from the root level tsconfig.

Author: alan-agius4

packages/angular_devkit/build_angular/test/hello-world-lib/projects/lib/tsconfig.lib.json

@@ -1,15 +1,10 @@
 {
   "extends": "../../tsconfig.json",
   "compilerOptions": {
-    "target": "es2015",
     "declaration": true,
     "declarationMap": true,
     "inlineSources": true,
-    "types": [],
-    "lib": [
-      "dom",
-      "es2018"
-    ]
+    "types": []
   },
   "exclude": [
     "src/test.ts",

packages/schematics/angular/library/files/tsconfig.lib.json.template

@@ -3,15 +3,10 @@
   "extends": "<%= relativePathToWorkspaceRoot %>/tsconfig.json",
   "compilerOptions": {
     "outDir": "<%= relativePathToWorkspaceRoot %>/out-tsc/lib",
-    "target": "es2015",
     "declaration": true,
     "declarationMap": true,
     "inlineSources": true,
-    "types": [],
-    "lib": [
-      "dom",
-      "es2018"
-    ]
+    "types": []
   },
   "exclude": [
     "src/test.ts",