fix(training): 移除课程底部按钮的宽度设置，优化样式

src/pages/training/index.vue

@@ -232,7 +232,6 @@ function startExam() {
   font-size: 20rpx;
 }
 .course-bottom button {
-  width: 120rpx;
   height: 46rpx;
   border-radius: 24rpx;
   background: #eaf3ff;