EPUB export dialog: fix wrong string context

I forgot to update this after copy&paste.

Change-Id: I5f060a602a35ee83bc3f2ff4898039bf347fe1cd
Reviewed-on: https://gerrit.libreoffice.org/45784Reviewed-by: Miklos Vajna <vmiklos@collabora.co.uk>
Tested-by: Jenkins <ci@libreoffice.org>

writerperfect/uiconfig/ui/exportepub.ui

@@ -422,7 +422,7 @@
                     <property name="visible">True</property>
                     <property name="can_focus">False</property>
                     <property name="margin_top">6</property>
-                    <property name="label" translatable="yes" context="exportepub|generalft">Metadata</property>
+                    <property name="label" translatable="yes" context="exportepub|metadataft">Metadata</property>
                     <property name="use_underline">True</property>
                     <property name="mnemonic_widget">versionlb</property>
                     <property name="xalign">0</property>