new-calendar: Clarify web calendar strings

Now that the "Open" button has been removed,
it is now a feature to "Connect" rather than "Import",
so update the section title to reflect that.

Also give a hint as to what protocols are supported.

src/gui/calendar-management/gcal-new-calendar-page.ui

@@ -60,7 +60,7 @@
                 <child>
                   <object class="GtkLabel">
                     <property name="hexpand">True</property>
-                    <property name="label" translatable="yes">Import a Calendar</property>
+                    <property name="label" translatable="yes">Connect to an Online Calendar</property>
                     <property name="xalign">0.0</property>
                     <attributes>
                       <attribute name="scale" value="1.3" />
@@ -77,7 +77,7 @@
                     <!-- Online Accounts reference label-->
                     <child>
                       <object class="GtkLabel">
-                        <property name="label" translatable="yes">Alternatively, enter the web address of an online calendar you want to import, or open a supported calendar file.</property>
+                        <property name="label" translatable="yes">HTTPS, CalDAV, or Webcal URLs are supported. Online calendars that can only be updated by the provider will be added as read-only.</property>
                         <property name="wrap">True</property>
                         <property name="xalign">0</property>
                         <layout>