This was missed in https://github.com/microsoft/playwright/pull/29131
Fixes the following error in java on windows:
```
Error: Cannot find module 'C:\Users\RUNNER~1\AppData\Local\Temp\playwright-java-910508779801292985\package\lib\cli\cli.js'
at Module._resolveFilename (node:internal/modules/cjs/loader:1144:15)
at Module._load (node:internal/modules/cjs/loader:985:27)
at Function.executeUserEntryPoint [as runMain] (node:internal/modules/run_main:135:12)
at node:internal/main/run_main_module:28:49 {
code: 'MODULE_NOT_FOUND',
requireStack: []
}
```
* It is more common to set env variable value without quotes on Windows
(see the bug)
* Use defined to check for string presence, it will work nicely with
strings that contain whitespaces
https://github.com/microsoft/playwright-java/issues/1213
