android: pan/bi: Remove combine lowering

Fixes the following building error:

clang: error: no such file or directory: 'external/mesa/src/panfrost/bifrost/bi_lower_combine.c'
clang: error: no input files

Fixes: 8b0d0a931b ("pan/bi: Remove combine lowering")
Signed-off-by: Mauro Rossi <issor.oruam@gmail.com>
Acked-by: Alyssa Rosenzweig <alyssa.rosenzweig@collabora.com>
Part-of: <https://gitlab.freedesktop.org/mesa/mesa/-/merge_requests/8294>

src/panfrost/Makefile.sources

@@ -4,7 +4,6 @@ bifrost_FILES := \
         bifrost/bifrost_compile.h \
         bifrost/bi_layout.c \
         bifrost/bi_liveness.c \
-        bifrost/bi_lower_combine.c \
         bifrost/bi_tables.c \
         bifrost/bi_schedule.c \
         bifrost/bi_special.c \