minor #45197 [Process] Update PHPDoc to use proper placeholder syntax (chrismcgehee)
minor #45197 [Process] Update PHPDoc to use proper placeholder syntax (chrismcgehee)

This PR was squashed before being merged into the 4.4 branch.

Discussion
----------

[Process] Update PHPDoc to use proper placeholder syntax

| Q             | A
| ------------- | ---
| Branch?       | 4.4
| Bug fix?      | no
| New feature?  | no
| Deprecations? | no
| Tickets       | no
| License       | MIT
| Doc PR        | no

I'd like to add this PHPDoc comment to help make sure `Process::fromShellCommandline` is used securely. The other day, one of the developers at my company wrote some code that was roughly like:
```php
$process = Process::fromShellCommandline('find $FILENAME');
$process->run(null, ['FILENAME' => $fileName]);
```
Since `$fileName` is user input, he thought he was doing the secure thing by using placeholders. The issue is that a malicious user could have utilized the `-exec` option of `find` to gain arbitrary code execution, for example `$fileName = '. -exec echo Foo! ;'`. This can be fixed by simply surrounding `$FILENAME` with double quotes because this passes the input as a single argument to `find` instead of passing it as multiple arguments. I believe there are enough programs out there that can be manipulated if an attacker is able to control multiple arguments that it's worth putting a warning here to help prevent the mistake of not surrounding placeholders with quotes.

Commits
-------

a2ecf08736 [Process] Update PHPDoc to use proper placeholder syntax

nicolas-grekas/symfony,zerkms/symfony,damienalexandre/symfony,mpdude/symfony,tucksaun/symfony,derrabus/symfony,curry684/symfony,curry684/symfony,xabbuh/symfony,d-ph/symfony,derrabus/symfony,mpdude/symfony,phramz/symfony,tucksaun/symfony,zerkms/symfony,d-ph/symfony,HeahDude/symfony,HeahDude/symfony,nicolas-grekas/symfony,damienalexandre/symfony,symfony/symfony,derrabus/symfony,nicolas-grekas/symfony,mpdude/symfony,tucksaun/symfony,tucksaun/symfony,damienalexandre/symfony,HeahDude/symfony,symfony/symfony,d-ph/symfony,mpdude/symfony,curry684/symfony,xabbuh/symfony,damienalexandre/symfony,stof/symfony,HeahDude/symfony,zerkms/symfony,sgehrig/symfony,stof/symfony,phramz/symfony,curry684/symfony,nicolas-grekas/symfony,sgehrig/symfony,symfony/symfony,stof/symfony,sgehrig/symfony,paradajozsef/symfony,stof/symfony,symfony/symfony,d-ph/symfony,sgehrig/symfony,paradajozsef/symfony,derrabus/symfony,xabbuh/symfony,phramz/symfony,paradajozsef/symfony,xabbuh/symfony,zerkms/symfony,paradajozsef/symfony,phramz/symfony