remove CSS rules that are very likely to be outdated

- performed a search for corresponding class names across OP core and multiple plugins and did not find occurences
- the comment refers to the cost plugin as source of those rules (which was among the tested plugins)

app/assets/stylesheets/_misc_legacy.sass

@@ -668,16 +668,6 @@ div.indent
 
 /*Cost-Plugin specific styles */
 
-.icon-pieces
-  background-image: image-url("webalys/units.png") !important
-
-.icon-pieces-time
-  background-image: image-url("webalys/time.png") !important
-
-body
-  &.theme-Bsp .buttons .apply, &.theme-Dtag .buttons .apply
-    background-color: #24b3e7
-
 input::-webkit-input-placeholder, :-moz-placeholder
   color: #000000
 
@@ -702,14 +692,6 @@ h4.comment
   img
     margin-right: 3px
 
-.atwho-view
-  z-index: 25
-  .cur
-    background: #FFFFBB
-    color: #4B4B4B
-    strong
-      color: black
-
 /*
  * Legacy headings to create headings which are similiar to the toolbar
  * but cannot use the toolbar yet (e.g Legacy forms)