remove material

Author: linux-china

src/main/frontend/src/styles.css

@@ -1,3 +1,2 @@
 /* You can add global styles to this file, and also import other style files */
-@import "~bootstrap/dist/css/bootstrap.min.css";
-@import '~@angular/material/prebuilt-themes/deeppurple-amber.css';
+@import "~bootstrap/dist/css/bootstrap.min.css";