revert: "fix(@schematics/angular): add skipLibCheck to workspace tsconfig"

This reverts commit a8c60cb.

Closes: #16696

Author: alan-agius4

packages/schematics/angular/workspace/files/tsconfig.json.template

@@ -8,7 +8,6 @@
     "noImplicitThis": true,
     "noFallthroughCasesInSwitch": true,
     "strictNullChecks": true,<% } %>
-    "skipLibCheck": true,
     "sourceMap": true,
     "declaration": false,
     "downlevelIteration": true,