core: 计量尝试人数而非提交量

suggested by @Menci

packages/ui-default/pages/problem_main.page.styl

@@ -10,23 +10,23 @@
     width: rem(140px)
     position: relative
 
-  .col--submit_n, .col--ac_rate, .col--difficulty
+  .col--tried, .col--ac, .col--difficulty
     width: rem(70px)
     text-align: center
 
   .col--status
     border-right: 1px solid $table-border-color
 
-  .col--submit_n, .col--difficulty
+  .col--tried, .col--difficulty
     border-left: 1px solid $table-border-color
 
   +mobile()
     .col--status,
-    .col--submit_n,
+    .col--tried,
     .col--difficulty
       display: none
 
-    .col--ac_rate
+    .col--ac
       border-left: 1px solid $table-border-color