Change version to 2.7.4

reg-app/Dockerfile

@@ -2,7 +2,7 @@ FROM alpine/git AS clone
 WORKDIR /app
 RUN git clone https://git.scc.kit.edu/simon/reg-app.git
 WORKDIR /app/reg-app
-RUN git checkout tags/2.7.3 -b branch-2.7.3
+RUN git checkout tags/2.7.4 -b branch-2.7.4
 
 FROM maven:3.6-openjdk-11-slim AS build