Fixed Project view .board-column height for tall screens. (go-gitea#22108)

This bug occurs because we are calculating `.board-column` height
strictly off of `vh`, when the layout header is of static height.

BEFORE


https://user-images.githubusercontent.com/24665/206991060-372c24e3-986e-4fc6-9fc8-aab8b4ef09bb.mp4


AFTER


https://user-images.githubusercontent.com/24665/206991070-91b7cbab-d807-4016-8696-e43bdaf8a7ff.mp4

Author: gnat

web_src/less/features/projects.less

@@ -12,7 +12,8 @@
   margin: 0 .5rem !important;
   padding: .5rem !important;
   width: 320px;
-  height: 60vh;
+  height: calc(100vh - 450px);
+  min-height: 60vh;
   overflow-y: scroll;
   flex: 0 0 auto;
   overflow: visible;