Update projectRoot in launchPackager.bat (#24115)

Summary:
`launchPackager.bat` starts metro server but does not pass projectRoot to it. So metro server starts in the wrong directory, It is because `startServerInNewWindow` pass `react-native` directory instead of `projectRoot` in the third argument of `spawn()` in `runAndroid.js`

Its working for people
See #23908 (comment)

[Android] [Fixed] - projectRoot in launchPackager.bat
Pull Request resolved: #24115

Differential Revision: D14597101

Pulled By: cpojer

fbshipit-source-id: fb4155b72e35062cfb41fe1b3ecca0e2b4e849ce

Author: Mr. Anonymous

scripts/launchPackager.bat

@@ -6,6 +6,6 @@
 @echo off
 title Metro Bundler
 call .packager.bat
-node "%~dp0..\cli.js" --reactNativePath ../ start
+node "%~dp0..\cli.js" --reactNativePath ../ --projectRoot ../../../ start
 pause
 exit