Commit Makefiles changes not build manpage for igb(4), accidentally

forgotten in r315742.

X-MFC with:	r311849, r315742
Pointyhat to:	ngie
Sponsored by:	Dell EMC Isilon

share/man/man4/Makefile

@@ -205,7 +205,6 @@ MAN=	aac.4 \
 	if_ipsec.4 \
 	ifmib.4 \
 	ig4.4 \
-	igb.4 \
 	igmp.4 \
 	iic.4 \
 	iicbb.4 \
@@ -650,7 +649,6 @@ MLINKS+=hme.4 if_hme.4
 MLINKS+=hpet.4 acpi_hpet.4
 MLINKS+=${_hptrr.4} ${_rr232x.4}
 MLINKS+=${_attimer.4} ${_i8254.4}
-MLINKS+=igb.4 if_igb.4
 MLINKS+=ip.4 rawip.4
 MLINKS+=ipfirewall.4 ipaccounting.4 \
 	ipfirewall.4 ipacct.4 \