Fix otp_mmi filegroup name

- Looks like a typo here, that is preventing this MMI from being
  exported during a build.

Change-Id: I05a98f93be1bc62f843fb8e144c08bc358b81f90

hw/bitstream/vivado/BUILD

diff --git a/hw/bitstream/vivado/BUILD b/hw/bitstream/vivado/BUILD
index 50936ff..5da3217 100644
--- a/hw/bitstream/vivado/BUILD
+++ b/hw/bitstream/vivado/BUILD
@@ -91,7 +91,7 @@
     name = "otp_mmi",
     testonly = True,
     srcs = [":fpga_nexus"],
-    output_group = "opt_mmi",
+    output_group = "otp_mmi",
     tags = ["manual"],
 )