Or HaChaim on Numbers 5:3/אור החיים על במדבר ה׳:ג׳

1 אשר אני שכן בתוכם, "that I dwell amongst." This rule applied only as long as G'd's presence was still in the Tabernacle. Once the Tabernacle had been dismantled so that the שכינה had moved, even people afflicted with צרעת were allowed in the camp (Menachot 95).