Fix svg colors in file list table (#17903)

* Fix svg colors in file list table

Turns out this can be fixed by just removing rules. Directory and file
icons have other rules that still make them color correctly.

* tweak color on file icons

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>

web_src/less/_repository.less

         .svg {
           margin-left: 3px;
           margin-right: 5px;
-          color: #777777;
 
           &.octicon-reply {
             margin-right: 10px;
           &.octicon-file-submodule {
             color: var(--color-primary);
           }
+
+          &.octicon-file,
+          &.octicon-file-symlink-file {
+            color: var(--color-secondary-dark-7);
+          }
         }
       }
 

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

   color: var(--color-secondary-dark-6);
 }
 
-.repository.file.list #repo-files-table tbody .svg.octicon-file-directory,
-.repository.file.list #repo-files-table tbody .svg.octicon-file-submodule {
-  color: #7c9b5e;
-}
-
 .repository.labels .ui.basic.black.label {
   background-color: #bbbbbb !important;
 }
   border-left-color: #888;
 }
 
-.repository.file.list #repo-files-table tbody .svg {
-  color: var(--color-secondary-dark-6);
-}
-
 .repository.release #release-list > li .detail .dot {
   background-color: #505667;
   border-color: #383c4a;