Use the word "second" instead of "sec"

No need to use use a short version; there's plenty of space.

CCBUG: 430259

src/konfigurator/walletconfigwidget.ui

@@ -59,7 +59,7 @@
                <string>&lt;p&gt;&lt;b&gt;Close wallet after a period of inactivity.&lt;/b&gt;&lt;br&gt;When a wallet is closed the password is needed to access it again.&lt;/p&gt;</string>
               </property>
               <property name="suffix">
-               <string> min</string>
+               <string> minutes</string>
               </property>
               <property name="minimum">
                <number>1</number>