Remove redundant type attribute

It already defaults to `text/css` if value is absent (in HTML5).

src/webui/www/private/views/installsearchplugin.html

@@ -1,4 +1,4 @@
-<style type="text/css">
+<style>
     #installSearchPluginContainer {
         margin: 10px;
     }

src/webui/www/private/views/search.html

@@ -1,4 +1,4 @@
-<style type="text/css">
+<style>
     #searchPattern {
         width: 500px;
         line-height: 2em;

src/webui/www/private/views/searchplugins.html

@@ -1,4 +1,4 @@
-<style type="text/css">
+<style>
     #searchPluginsContainer {
         height: calc(100% - 20px);
         margin: 10px;