get rid of 'browser.startup.blankWindow'

docs/Changelog.md

@@ -10,11 +10,13 @@ Setting versions are documented using the pref `librewolf.cfg.version`, availabl
 **References**:
 
 - thumbnails are only used in privileged code to populate New Tab Page and Ctrl+Tab previews.
+- the startup blank window doesn't break anything and the perceived performance boost is irrelevant on modern hardware.
 
 #### Removed preferences
 
 ```
 defaultPref("browser.pagethumbnails.capturing_disabled", true);
+defaultPref("browser.startup.blankWindow", false);
 ```
 
 # 7.4

librewolf.cfg

@@ -148,7 +148,6 @@ defaultPref("browser.urlbar.speculativeConnect.enabled", false);
 defaultPref("privacy.resistFingerprinting", true);
 // rfp related settings
 defaultPref("privacy.resistFingerprinting.block_mozAddonManager", true); // prevents rfp from breaking AMO
-defaultPref("browser.startup.blankWindow", false); // if set to true it breaks RFP windows resizing
 defaultPref("browser.display.use_system_colors", false); // default, except Win
 /**
  * increase the size of new RFP windows for better usability, while still using a rounded value.