Fix shields setting in private is weird

When content setting's IncognitoBehavior is INHERIT_IF_LESS_PERMISSIVe,
normal profiles setting is modified when incognito profile's content settings
are initialized. Because of this behavior, sometimes shields are off and shields's
default configurations are different with normal window.
With INHERIT_IN_INCOGNITO, private windows uses normal windows' configuration w/o
modification.

chromium_src/components/content_settings/core/browser/content_settings_registry.cc

@@ -28,7 +28,7 @@ void ContentSettingsRegistry::BraveInit() {
                     CONTENT_SETTING_DETECT_IMPORTANT_CONTENT),
       WebsiteSettingsInfo::SINGLE_ORIGIN_WITH_EMBEDDED_EXCEPTIONS_SCOPE,
       WebsiteSettingsRegistry::DESKTOP,
-      ContentSettingsInfo::INHERIT_IF_LESS_PERMISSIVE,
+      ContentSettingsInfo::INHERIT_IN_INCOGNITO,
       ContentSettingsInfo::EPHEMERAL);
 }