docs(table): remove duplicate css in the table-filtering-example (angular#6935)

Author: Teamop

src/material-examples/table-filtering/table-filtering-example.css

@@ -5,14 +5,6 @@
   min-width: 300px;
 }
 
-.example-header {
-  min-height: 64px;
-  display: flex;
-  align-items: center;
-  padding-left: 24px;
-  font-size: 20px;
-}
-
 .example-header {
   min-height: 64px;
   display: flex;