room-history: Apply system monospace font to code blocks and event source

data/resources/stylesheet/_room_history.scss

@@ -208,7 +208,6 @@ message-sender {
   .codeview {
     border-radius: vendor.$menu_radius;
     padding: 6px;
-    font-family: monospace;
     background-color: var(--text-view-bg);
     color: var(--view-fg-color);
   }

data/resources/stylesheet/_session_view.scss

@@ -201,11 +201,6 @@ sidebar {
   font-size: 1.6em;
 }
 
-// Event details dialog
-.event-details-dialog .sourceview {
-  font-family: monospace;
-}
-
 // Account settings
 .account-settings listview {
 	background: transparent;

src/session/view/content/room_history/message_row/text/widgets.rs

@@ -409,7 +409,7 @@ fn widget_for_preformatted_text(
     let view = sourceview::View::builder()
         .buffer(&buffer)
         .editable(false)
-        .css_classes(["codeview", "frame"])
+        .css_classes(["codeview", "frame", "monospace"])
         .hexpand(true)
         .build();
 

src/session/view/event_details_dialog.ui

@@ -49,7 +49,7 @@
                                     <property name="xalign">0</property>
                                     <style>
                                       <class name="heading"/>
-                                    </style>        
+                                    </style>
                                   </object>
                                 </child>
                                 <child>
@@ -159,7 +159,7 @@
                                     <property name="xalign">0</property>
                                     <style>
                                       <class name="heading"/>
-                                    </style>        
+                                    </style>
                                   </object>
                                 </child>
                                 <child>
@@ -249,6 +249,9 @@
                         <property name="right-margin">12</property>
                         <property name="top-margin">12</property>
                         <property name="bottom-margin">12</property>
+                        <style>
+                          <class name="monospace"/>
+                        </style>
                       </object>
                     </property>
                   </object>