media: ext-ctrls-jpeg.rst: cleanup V4L2_CID_JPEG_COMPRESSION_QUALITY text

The text is repeating the name of the control, which causes
it to be displayed outside the page with PDF output.

Besides that, this is the only JPEG control doing that. Removing
the name duplication doesn't affect the description, but, instead,
make it nicer.

Signed-off-by: Mauro Carvalho Chehab <mchehab+huawei@kernel.org>