Fix Repeater Bits Definition

There appears to have been a copy-paste error, resulting in the down link definition labeling a bit as U_p instead of D_p

.gitlab-ci.yml

+build:
+  image: ctornau/latex
+  stage: build
+  artifacts:
+    paths:
+      - standard.pdf
+  script:
+    - latexmk -shell-escape -pdf standard.tex