Cleanup: CrOS network Settings: Remove unnecessary shared md-select include.

Elements that use md-select are already directly including such style.

Bug: None
Cq-Include-Trybots: master.tryserver.chromium.linux:closure_compilation
Change-Id: Ib7ac481f19a76ea46958220f66acb8c4b4f32543
Reviewed-on: https://chromium-review.googlesource.com/1048947Reviewed-by: Michael Giuffrida <michaelpg@chromium.org>
Commit-Queue: Demetrios Papadopoulos <dpapad@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557058}

ui/webui/resources/cr_components/chromeos/network/network_shared_css.html

 <link rel="import" href="chrome://resources/cr_elements/shared_style_css.html">
-<link rel="import" href="chrome://resources/html/md_select_css.html">
 
  <!-- Common styles for network elements. -->
 
 <dom-module id="network-shared">
   <template>
-    <style include="cr-shared-style md-select">
+    <style include="cr-shared-style">
       :root {
         /* Margin for the show/hide password icon */
         --network-control-margin: 40px;