[FIX] l10n_ch: isr report with report refactoring

Report refactoring and f29df7fb2e expect when printing document that the
current one is in variable `o`, so this commit enables it.

opw-1894243
closes #28143

Co-authored-by: Laurent Smet <smetl@users.noreply.github.com>

addons/l10n_ch/report/isr_report.xml

@@ -153,6 +153,7 @@
         <template id="l10n_ch.isr_report_main">
             <t t-call="web.html_container">
                 <t t-foreach="docs" t-as="invoice">
+                    <t t-set="o" t-value="invoice"/>
                     <t t-call="l10n_ch.l10n_ch_isr_report_template"/>
                 </t>
             </t>