[FIX] web: titles are smaller in reports

Since the Bootstrap 5 migration the "headings" `<h1>`, `<h2>`, ... are
smaller than before.

This commit, restores the old CSS rules from Bootstrap 4 for reports.

Steps to reproduce:
* Open Sales
* Select a quotation
* Print the Quotation (using Print dropdown) => BUG title is smaller
  than the old version of Odoo (e.g. Odoo v15)

closes odoo/odoo#106668

Signed-off-by: Adrien Dieudonné (adr) <adr@odoo.com>

addons/web/static/src/webclient/actions/reports/report.scss

@@ -13,6 +13,36 @@ body {
     font-family: $o-default-report-font;
 }
 
+h1, h2, h3, h4, h5, h6, .h1, .h2, .h3, .h4, .h5, .h6 {
+    margin-bottom: 0.5rem;
+    font-weight: 500;
+    line-height: 1.2;
+}
+
+h1, .h1 {
+    font-size: 2.5rem;
+}
+
+h2, .h2 {
+    font-size: 2rem;
+}
+
+h3, .h3 {
+    font-size: 1.75rem;
+}
+
+h4, .h4 {
+    font-size: 1.5rem;
+}
+
+h5, .h5 {
+    font-size: 1.25rem;
+}
+
+h6, .h6 {
+    font-size: 1rem;
+}
+
 p, span, strong, em {
     line-height: 1.5;
 }