clean: remove redundant allImportedFiles check in _onwrite (#346)

- this checks if any of the files in `parsedConfig.fileNames` are _not_
  in `allImportedFiles`, but all the files in `parsedConfig.fileNames`
  are explicitly added in the `options` hook on line 98
  - so this is redundant / dead code; the check will never be true

- this can be considered a remnant of an old bug as an old commit fixed
  a bug with `allImportedFiles` after it was released:
  f24359e

src/index.ts

@@ -306,11 +306,6 @@ const typescript: PluginImpl<RPT2Options> = (options) =>
 				const key = normalize(name);
 				if (key in declarations)
 					return;
-				if (!allImportedFiles.has(key))
-				{
-					context.debug(() => `skipping declarations for unused '${key}'`);
-					return;
-				}
 
 				context.debug(() => `generating missed declarations for '${key}'`);
 				const output = service.getEmitOutput(key, true);