Fix fava build commands

`find` seems to behave extremely weird within Docker `RUN` commands.
I could not find a way to properly escape `;`s in a way that I
can specify one for `find -exec` and a second one to separate `find`
from the next command. `find` would always complain about it.

So instead, it's now simply the last command in the chain, where no
separator is needed.

images/fava/Dockerfile

@@ -41,8 +41,8 @@ RUN set -eux; \
     pip3 install -U /tmp/build/fava; \
     pip3 install -r requirements.txt; \
     pip3 uninstall -y pip; \
-    find /app -name __pycache__ -exec rm -rf -v {} + \;; \
-    rm -r /app/share;
+    rm -r /app/share; \
+    find /app -name __pycache__ -exec rm -rf -v {} +
 
 FROM python:3.12.5-slim
 COPY --from=build_env /app /app