You can try to apply css like,
tbody .tr:nth-child(2) {
page-break-after: always;
}
or
tbody tr{
page-break-inside: avoid;
page-break-after: auto;
}

This is my code i can't figure it out

<tbody>
<t t-set="i" t-value="1"/>
<t t-set="counter" t-value="0"/>
<t t-foreach="o.line_ids" t-as="line">

<tr class="text-center">

<td>

<span t-esc="i"/>
<t t-set="i" t-value="i+1"/>
</td>
<td>
<span t-field="line.matricule_cnss"/>
</td>
<td>
<span t-field="line.employee_name"/>
</td>
<td>
<span t-field="line.num_chezemployeur"/>
</td>
<td>
</td>
<td>
<span t-field="line.premier_mois"/>
</td>
<td>
<span t-field="line.deuxieme_mois"/>
</td>
<td>
<span t-field="line.troisieme_mois"/>
</td>
<td>
<span t-field="line.tot_gen"/>
</td>
<t t-if="counter == 2">
<p style="page-break-before;"> </p>
<t t-set="counter" t-value="0"/>
</t>
<t t-set="counter" t-value="counter + 1" />
</tr>

</t>
</tbody>