docs/releasing: tweak the glxinfo/glxgear/etc. command lines
docs/releasing: tweak the glxinfo/glxgear/etc. command lines

Print only the information needed. Namely:
*info: the DRI module picked and the vendor/renderer strings
*gears: everything but the "...configuration file..." line(s)

v2: (Eric) Use "2>&1 |" over "|&", properly escape &.

Signed-off-by: Emil Velikov <f20878473f414da183da19ee25c8722cc1d711e4@collabora.com>

metora/MesaGLSLCompiler,metora/MesaGLSLCompiler,metora/MesaGLSLCompiler