Removed unused CSS in admin.

.system-message, .system-message-title are unused since their
introduction in ce0d0cd9e2cd5ac9850d825f28db39b1e123ac1e.
.float-right, .float-left, .align-left, .align-right, and .example are
unused since 6eb4f2569266391e223410ab7eaa2555ac0a4f10.

django/contrib/admin/static/admin/css/base.css

@@ -173,22 +173,10 @@ hr {
     font-size: 11px;
 }
 
-.tiny {
-    font-size: 10px;
-}
-
-p.tiny {
-    margin-top: -2px;
-}
-
 .mini {
     font-size: 10px;
 }
 
-p.mini {
-    margin-top: -3px;
-}
-
 .help, p.help, form p.help, div.help, form div.help, div.help li {
     font-size: 11px;
     color: #999;
@@ -211,32 +199,10 @@ p img, h1 img, h2 img, h3 img, h4 img, td img {
     font-weight: normal;
 }
 
-.float-right {
-    float: right;
-}
-
-.float-left {
-    float: left;
-}
-
 .clear {
     clear: both;
 }
 
-.align-left {
-    text-align: left;
-}
-
-.align-right {
-    text-align: right;
-}
-
-.example {
-    margin: 10px 0;
-    padding: 5px 10px;
-    background: #efefef;
-}
-
 .nowrap {
     white-space: nowrap;
 }
@@ -630,20 +596,6 @@ td ul.errorlist + input, td ul.errorlist + select, td ul.errorlist + textarea {
     border: 1px solid #ba2121;
 }
 
-div.system-message {
-    background: #ffc;
-    margin: 10px;
-    padding: 6px 8px;
-    font-size: .8em;
-}
-
-div.system-message p.system-message-title {
-    padding: 4px 5px 4px 25px;
-    margin: 0;
-    color: #c11;
-    background: #ffefef url(../img/icon-no.svg) 5px 5px no-repeat;
-}
-
 .description {
     font-size: 12px;
     padding: 5px 0 0 12px;