fix(ngc): Revert "fix(ngc): add an option to produce TS1.9-pathMapping imports (#10602)" (#10765)

This reverts commit beadf6167a.

tools/@angular/tsc-wrapped/src/options.ts

@@ -18,18 +18,6 @@ interface Options extends ts.CompilerOptions {
 
   // Whether to embed debug information in the compiled templates
   debug?: boolean;
-
-  // Starting with TypeScript 1.9, the 'rootDirs' option can be used
-  // to allow multiple source directories to have relative imports
-  // between them.
-  // This option causes generated code to use imports relative to the
-  // current directory, and requires you configure the 'rootDirs' to
-  // include both the genDir and rootDir.
-  // However, due to https://github.com/Microsoft/TypeScript/issues/8245
-  // note that using this option does not lay out into a flat directory
-  // with application and generated sources side-by-side, so you must
-  // teach your module loader how to resolve such imports as well.
-  writeImportsForRootDirs?: boolean;
 }
 
 export default Options;