MAINTAINERS: Remove Vincent Abriou for STM/STI DRM drivers.

Remove Vincent Abriou's email as he has no more review activities on
STM/STI DRM drivers.

Signed-off-by: Patrice Chotard <patrice.chotard@foss.st.com>
Cc: Vincent Abriou <vincent.abriou@st.com>
Link: https://lore.kernel.org/r/20210216074929.29033-3-patrice.chotard@foss.st.com

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Signed-off-by: Arnd Bergmann <arnd@arndb.de>