Revert "desktop: fix loplugin:oncevar"

This reverts commit 8dc2873081bff3fe7107d472a91a24af8b67a87d. Instead of
working around the warning, the plugin will be disabled, as its warnings
are not useful in all cases.
diff --git a/desktop/source/lib/init.cxx b/desktop/source/lib/init.cxx
index 0d0cdf2..ab765dc 100644
--- a/desktop/source/lib/init.cxx
+++ b/desktop/source/lib/init.cxx
@@ -2007,7 +2007,7 @@ static void lo_setDocumentPassword(LibreOfficeKit* pThis,

static char* lo_getVersionInfo(LibreOfficeKit* /*pThis*/)
{
    static const OUString sVersionStrTemplate(
    const OUString sVersionStrTemplate(
        "{ "
        "\"ProductName\": \"%PRODUCTNAME\", "
        "\"ProductVersion\": \"%PRODUCTVERSION\", "