fix: release writing header (#245)

Author: Y-k-Y

src/frontend/styles/components/writing.pcss

@@ -1,6 +1,4 @@
 .writing-header {
-  position: sticky;
-  top: 0;
   padding: 15px 0;
   margin-top: calc(-1 * var(--layout-padding-vertical));
   background: #fff;