Move pipelines test trace styles to page bundle

In order to make the global css file (pipelines.scss) smaller, this
change moves the pipeline tests trace styles to the page bundle scss
file.

app/assets/stylesheets/framework/mixins.scss

@@ -215,7 +215,7 @@
   }
 
   &.build-trace-rounded {
-    border-radius: $border-radius-base;
+    border-radius: $gl-border-radius-base;
   }
 }
 

app/assets/stylesheets/page_bundles/pipeline.scss

@@ -476,3 +476,9 @@
     height: auto !important;
   }
 }
+
+.test-reports-table {
+  .build-trace {
+    @include build-trace();
+  }
+}

app/assets/stylesheets/pages/pipelines.scss

@@ -130,12 +130,6 @@
   float: none;
 }
 
-.test-reports-table {
-  .build-trace {
-    @include build-trace();
-  }
-}
-
 .progress-bar.bg-primary {
   background-color: $blue-500 !important;
 }