update text for new and restoring seeds

src/newseed.ui

@@ -17,7 +17,7 @@
    <item row="0" column="0">
     <widget class="QLabel" name="label">
      <property name="text">
-      <string>This is your new wallet's seed phrase. PLEASE BACK IT UP SECURELY.</string>
+      <string>This is your new wallet's seed phrase. PLEASE BACK IT UP SECURELY. Write it on paper. Do not store it anywhere others can access it.</string>
      </property>
      <property name="wordWrap">
       <bool>true</bool>

src/restoreseed.ui

@@ -62,7 +62,7 @@
          </font>
         </property>
         <property name="text">
-         <string>Wallet birthday is the block height at which the wallet had the first transaction. If you don't know this, you can leave it as &quot;0&quot; (It'll take longer to rescan)</string>
+         <string>Wallet birthday is the block height at which the wallet had the first transaction. If you don't know this, you can leave the default. (It'll take longer to rescan)</string>
         </property>
         <property name="wordWrap">
          <bool>true</bool>