Match arc-green code tag color to code blocks (#11023)

Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: techknowlogick <techknowlogick@gitea.io>

web_src/less/themes/theme-arc-green.less

@@ -1586,7 +1586,7 @@ body .xdsoft_datetimepicker {
 
 .markdown:not(code) code,
 .markdown:not(code) tt {
-    background-color: rgba(0, 0, 0, .12);
+    background-color: #2a2e3a;
 }
 
 footer .container .links > * {