settings: Remove unnecessary form-horizontal class.

This commit removes form-horizontal class from form
elements in alert-words, realm-exports and user-privacy
pages.

We can safely remove this class since there is no select,
input, help-inline or input-append child elements for these
and thus this class is not used for applying any CSS rules.

static/templates/settings/account_settings.hbs

@@ -82,7 +82,7 @@
 
         <hr class="settings_separator" />
 
-        <div class="form-horizontal" id="api_key_button_box">
+        <div id="api_key_button_box">
             <h3>{{t "API key" }}</h3>
 
             <div class="input-group">

static/templates/settings/alert_word_settings.hbs

@@ -1,5 +1,5 @@
 <div id="alert-word-settings" class="settings-section" data-name="alert-words">
-    <form class="form-horizontal" id="alert_word_info_box">
+    <form id="alert_word_info_box">
         <p class="alert-word-settings-note">
             {{t "Alert words allow you to be notified as if you were @-mentioned when certain words or phrases are used in Zulip. Alert words are not case sensitive."}}
         </p>

static/templates/settings/data_exports_admin.hbs

@@ -19,7 +19,7 @@
     <div class="alert" id="export_status" role="alert">
         <span class="export_status_text"></span>
     </div>
-    <form class="form-horizontal">
+    <form>
         <div class="add-new-export-box grey-box">
             <div class="wrapper">
                 <button type="submit" class="button rounded sea-green" id="export-data">