[gimp-help] quickreference: fix unmatched XML tag in Norwegian translation.

[Jehan <jehanp src gnome org>]

commit 80b08070338afe67b3e47d3e883aeac4f1563a67
Author: Jehan <jehan girinstud io>
Date:   Sat Jun 5 23:17:45 2021 +0200

    quickreference: fix unmatched XML tag in Norwegian translation.
    
    Not sure why the first build worked, but subsequent builds failed (maybe
    there is something wrong with the order of actions?). In any case, the
    build fails with:
    
    > xml/gimp-keys-nn.xml:2: parser error : Start tag expected, '<' not found
    
    And the reason is because the XML actually starts with an error message
    instead of the usual <?xml?> header:
    
    ========================
    Source xml: /home/jehan/dev/src/gimp-help/quickreference/gimp-keys.xml
    Source po : /home/jehan/dev/src/gimp-help/quickreference/po/nn.po
    
    Translated msgstr:
    Du kan også aktivere menyane ved å halde nede <Alt>-tasten samstundes som du trykker den bokstaven som er 
understreka i menynamnet.
    
    ERROR: Found unmatched tags in po msgstr.
    Tags not matched: ['Alt']
    ========================
    
    Since the translated content indeed expects possible XML tags,
    translators should not use < and > randomly.
    Moreover I tested <alt/> as it is used in other places, but the
    generated SVG does not display the Alt key image, so I guess this tag
    only works in specific fields. Anyway since the source was not using an
    XML tag either, let's just stick to simply writing Alt normally.

 quickreference/po/nn.po | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/quickreference/po/nn.po b/quickreference/po/nn.po
index 2ecc2a18e..bc5a22c7a 100644
--- a/quickreference/po/nn.po
+++ b/quickreference/po/nn.po
@@ -589,7 +589,7 @@ msgid ""
 "Menus can also be activated by Alt with the letter underscored in the menu "
 "name."
 msgstr ""
-"Du kan også aktivere menyane ved å halde nede <Alt>-tasten samstundes som du "
+"Du kan også aktivere menyane ved å halde nede Alt-tasten samstundes som du "
 "trykker den bokstaven som er understreka i menynamnet."
 
 #: gimp-keys.xml:321(action)