ui: Allow underlining for most links due to Bootstrap 5

- Bootstrap 5 underlines all links by default. Allow this change without
reverting as this is likely done to improve accessibility.

- In Networks diagram and firewall page, provide exception and remove the
underlining.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: Veiko Aasa <veiko17@disroot.org>

plinth/modules/firewall/static/firewall.css

@@ -3,6 +3,7 @@
 */
 
 a.dropdown-toggle {
+    text-decoration: none;
     color: black;
 }
 

plinth/modules/networks/static/networks.css

@@ -32,6 +32,10 @@
     margin-bottom: 2rem;
 }
 
+.connection-diagram a {
+    text-decoration: none;  /* Not important so make them less noisy */
+}
+
 .col-image {
     display: block;
     width: 100%;