Minor refactor

Dockerfile

@@ -248,10 +248,8 @@ RUN mkdir -pm755 /etc/apt/preferences.d && \
 Pin: version 1:1snap*\n\
 Pin-Priority: -1" > /etc/apt/preferences.d/firefox-nosnap && \
     # Add Mozilla Firefox PPA
-    mkdir -pm755 /etc/apt/trusted.gpg.d && \
-    curl -fsSL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x0AB215679C571D1C8325275B9BDB3D89CE49EC21" | gpg --dearmor -o /etc/apt/trusted.gpg.d/mozillateam-ubuntu-ppa.gpg && \
-    mkdir -pm755 /etc/apt/sources.list.d && \
-    echo "deb https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu $(grep UBUNTU_CODENAME= /etc/os-release | cut -d= -f2) main" > "/etc/apt/sources.list.d/mozillateam-ubuntu-ppa-$(grep UBUNTU_CODENAME= /etc/os-release | cut -d= -f2).list" && \
+    mkdir -pm755 /etc/apt/trusted.gpg.d && curl -fsSL "https://keyserver.ubuntu.com/pks/lookup?op=get&search=0x0AB215679C571D1C8325275B9BDB3D89CE49EC21" | gpg --dearmor -o /etc/apt/trusted.gpg.d/mozillateam-ubuntu-ppa.gpg && \
+    mkdir -pm755 /etc/apt/sources.list.d && echo "deb https://ppa.launchpadcontent.net/mozillateam/ppa/ubuntu $(grep UBUNTU_CODENAME= /etc/os-release | cut -d= -f2) main" > "/etc/apt/sources.list.d/mozillateam-ubuntu-ppa-$(grep UBUNTU_CODENAME= /etc/os-release | cut -d= -f2).list" && \
     apt-get update && apt-get install --no-install-recommends -y \
         kde-plasma-desktop \
         adwaita-icon-theme-full \