build: clarify which locale files are included

related: 2cb4e56be3

contrib/build-linux/appimage/build.sh

@@ -109,6 +109,8 @@ info "preparing electrum-locale."
     if ! which msgfmt > /dev/null 2>&1; then
         fail "Please install gettext"
     fi
+    # we want the binary to have only compiled (.mo) locale files; not source (.po) files
+    rm -rf "$PROJECT_ROOT/electrum/locale/"
     for i in ./locale/*; do
         dir="$PROJECT_ROOT/electrum/$i/LC_MESSAGES"
         mkdir -p $dir