Merge pull request #15782 from opensourcerouting/fix/drop_srte_color_flag

bgpd: Drop SRTE_COLOR attribute flag

diff --cc bgpd/bgp_attr.h
Simple merge

diff --cc bgpd/bgp_routemap.c
Simple merge

diff --cc bgpd/bgp_zebra.c
Simple merge

diff --cc bgpd/bgpd.h
Simple merge