Fix font-size in inline code comment preview (#35209)

Previously, when writing a inline code comment, the markup preview would
have incorrect font size of 16px. This fixes it to 14px and also
combines similar CSS rules into one.

I'm not a fan of this selector complexity, but it seems like a necessity
because standalone markup files render at 16px while comments render at
14px.

---------

Signed-off-by: silverwind <me@silverwind.io>

Author: silverwind

web_src/css/markup/content.css

@@ -1,6 +1,6 @@
 .markup {
   overflow: hidden;
-  font-size: 16px;
+  font-size: 14px; /* 14px for comments, overridden to 16px for .file-view below. */
   line-height: 1.5 !important;
   overflow-wrap: break-word;
 }
@@ -318,6 +318,7 @@ In markup content, we always use bottom margin for all elements */
 
 .file-view.markup {
   padding: 1em 2em;
+  font-size: 16px;
 }
 
 .file-view.markup:has(.file-not-rendered-prompt) {

web_src/css/repo.css

@@ -300,10 +300,6 @@ td .commit-summary {
   min-width: 100px;
 }
 
-.repository.new.issue .comment.form .content .markup {
-  font-size: 14px;
-}
-
 .repository.view.issue .instruct-toggle {
   display: inline-block;
 }
@@ -630,10 +626,6 @@ td .commit-summary {
   background: var(--color-light);
 }
 
-.repository.view.issue .comment-list .comment .markup {
-  font-size: 14px;
-}
-
 .repository.view.issue .comment-list .comment .no-content {
   color: var(--color-text-light-2);
   font-style: italic;
@@ -723,10 +715,6 @@ td .commit-summary {
   text-align: center;
 }
 
-.repository.compare.pull .markup {
-  font-size: 14px;
-}
-
 .repository.branches .commit-divergence .bar-group {
   position: relative;
   float: left;