GUACAMOLE-1364: Correct rendering of SSO provider list during invalid login animation.

The SSO provider list unexpectedly shrinks when the invalid login
"shake" animation plays due to the use of "display: table-row" vs. the
login form's own use of "display: table-cell". Migrating the SSO
provider list to a simple absolutely-positioned div corrects this and
matches the way the Guacamole version is rendered.

extensions/guacamole-auth-sso/modules/guacamole-auth-sso-base/src/main/resources/html/sso-providers.html

@@ -1,7 +1,5 @@
 <meta name="after" content=".login-ui .login-dialog-middle">
 <div class="sso-providers">
-    <div class="sso-providers-content">
-        {{ 'LOGIN.SECTION_HEADER_SSO_OPTIONS' | translate }}
-        <ul class="sso-provider-list"></ul>
-    </div>
+    {{ 'LOGIN.SECTION_HEADER_SSO_OPTIONS' | translate }}
+    <ul class="sso-provider-list"></ul>
 </div>