Lower the battery threshold to 30% and default the cachy-update prompt to yes

The prompt offering to silence cachy-update's own update notification now
defaults to yes: once updates install themselves that notification is nothing
but noise, so the common answer should be the one you get by pressing Enter.

It also accepts "j" now. The prompt is translated, so a German user reads
"[J/n]" and types the German letter - which the old check for "y" alone
silently read as a refusal.

po/cachy-auto-update.pot

@@ -168,7 +168,7 @@ msgstr ""
 msgid "base-devel is missing - AUR packages cannot be built without it."
 msgstr ""
 
-msgid "cachy-update also notifies about available updates. Turn its notifications off? [y/N]"
+msgid "cachy-update also notifies about available updates. Turn its notifications off? [Y/n]"
 msgstr ""
 
 msgid "cachy-update's update check has been disabled."