Fix firefox fingerprint protection.

ansible/roles/firefox/defaults/main.yaml

@@ -33,7 +33,7 @@ firefox_config:
   browser.urlbar.speculativeConnect.enabled: false
   # Do not resist fingerprinting because that tells websites to use light mode.
   # https://bugzilla.mozilla.org/show_bug.cgi?id=1732114
-  privacy.resistFingerprinting: true
+  privacy.resistFingerprinting: null # (default false)
   # Instead, enable fingerprinting protection, which allows configuring an override.
   privacy.fingerprintingProtection: true
   # Allow sending dark mode preference to websites.

ansible/roles/firefox/tasks/peruser.yaml

@@ -10,12 +10,21 @@
   register: firefox_about_config
 
 - name: Configure Firefox about:config
+  when: item[1].value != None
   lineinfile:
     path: "{{ item[0].path }}"
     regexp: '"{{ item[1].key }}", [^")\n]*\)'
     line: 'user_pref("{{ item[1].key }}", {{ item[1].value | to_json }});'
   loop: "{{ firefox_about_config.files | product(firefox_config | dict2items) | list }}"
 
+- name: Configure Firefox about:config
+  when: item[1].value == None
+  lineinfile:
+    path: "{{ item[0].path }}"
+    regexp: '"{{ item[1].key }}", [^")\n]*\)'
+    state: absent
+  loop: "{{ firefox_about_config.files | product(firefox_config | dict2items) | list }}"
+
 - import_tasks: tasks/peruser_freebsd.yaml
   when: 'os_flavor == "freebsd"'