gcc-plugins: remove duplicate include in gcc-common.h

'tree-ssa-operands.h' included in 'gcc-common.h' is duplicated.
it's also included at line 56.

Reported-by: Zeal Robot <zealci@zte.com.cn>
Signed-off-by: Ye Guojin <ye.guojin@zte.com.cn>
Signed-off-by: Kees Cook <keescook@chromium.org>
Link: https://lore.kernel.org/r/20211019082910.998257-1-ye.guojin@zte.com.cn