minor symfony#17448 [Process] Remove a misleading comment (jakzal)

This PR was merged into the 2.3 branch.

Discussion
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[Process] Remove a misleading comment

| Q             | A
| ------------- | ---
| Bug fix?      | no
| New feature?  | no
| BC breaks?    | no
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | symfony#17387
| License       | MIT
| Doc PR        | -

The described behaviour was never implemented as part of symfony#3681.

Commits
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71f4a32 [Process] Remove a misleading comment

Author: Tobion

src/Symfony/Component/Process/Process.php

@@ -201,9 +201,6 @@ public function run($callback = null)
      * The callback receives the type of output (out or err) and some bytes from
      * the output in real-time while writing the standard input to the process.
      * It allows to have feedback from the independent process during execution.
-     * If there is no callback passed, the wait() method can be called
-     * with true as a second parameter then the callback will get all data occurred
-     * in (and since) the start call.
      *
      * @param callback|null $callback A PHP callback to run whenever there is some
      *                                output available on STDOUT or STDERR