[BUGFIX] Adjust comment for default HTTP-userAgent

The default userAgent is for example TYPO3/6.2.4

Change-Id: I2412b901a3a42938a433e7d8a414de24587011a3
Resolves: #60365
Releases: 6.3, 6.2
Reviewed-on: http://review.typo3.org/31735
Reviewed-by: Christian Kuhn <lolli@schwarzbu.ch>
Tested-by: Christian Kuhn <lolli@schwarzbu.ch>