misc (#1040)

* misc

- cleanup of old release notation in comments: e.g. if it's not applicable to ESR78+
- same with default version info
- simplify and save bytes on section 4700
- update 4500 header
  - and unify the message about using extensions as counterproductive
- letterboxing
   - provide info on stepped ranged (and drop crap about FF67)
   - don't judge users who dislike seeing margins (I don't like them either, but I force my window to exact dimensions and stay there)
- screenshots uploading was disabled in FF67+ : [67 release notes](https://www.mozilla.org/en-US/firefox/67.0/releasenotes/)
   - the pref is still there (default false) but so far I'm 99% sure this pref now does anything
   - I will add it to the scatchpad script if this change sticks

* simplify 4500 RFP, see #1041

* update removed script

* tidy readme, see #1045

- also put readme before releases

* RIP FX Site Compat

* clean out RFP Alts info: the information is redundant: it's already in the readme

scratchpad-scripts/arkenfox-clear-removed.js

@@ -1,7 +1,7 @@
 /***
  This will reset the preferences that have been removed completely from the arkenfox user.js.
 
- Last updated: 2-Oct-2020
+ Last updated: 18-Oct-2020
 
  For instructions see:
  https://github.com/arkenfox/user.js/wiki/3.1-Resetting-Inactive-Prefs-[Scripts]
@@ -225,6 +225,10 @@
     'browser.urlbar.usepreloadedtopurls.enabled',
     /* 80 */
     'dom.IntersectionObserver.enabled',
+    /* 82-beta */
+    'extensions.screenshots.upload-disabled',
+    'security.ssl3.dhe_rsa_aes_128_sha',
+    'security.ssl3.dhe_rsa_aes_256_sha',
     /* reset parrot: check your open about:config after running the script */
     '_user.js.parrot'
   ]