Removed obsolete classes from buttons in preferences.js

".wideButton" was removed from addfunds, copyButton, advancedSettings

Auditors: @bsclifton

Test Plan:
1. Open about:preferences#payments
2. Make sure the width of "Add funds..." and "Advanced Settings..." button is not affected with the change
3. Click "Advanced Settings..."
4. Click "Backup your wallet"
5. Make sure the width of two "Copy" buttons is not affected with the change

js/about/preferences.js

@@ -925,7 +925,7 @@ class PaymentsTab extends ImmutableComponent {
     const onButtonClick = this.props.ledgerData.get('created')
       ? this.props.showOverlay.bind(this, 'addFunds')
       : (this.props.ledgerData.get('creating') ? () => {} : this.createWallet)
-    return <Button l10nId={buttonText} className='primaryButton wideButton addFunds' onClick={onButtonClick.bind(this)} disabled={this.props.ledgerData.get('creating')} />
+    return <Button l10nId={buttonText} className='primaryButton addFunds' onClick={onButtonClick.bind(this)} disabled={this.props.ledgerData.get('creating')} />
   }
 
   get paymentHistoryButton () {
@@ -1088,7 +1088,7 @@ class PaymentsTab extends ImmutableComponent {
         <span data-l10n-id='ledgerBackupContent' />
         <div className='copyKeyContainer'>
           <div className='copyContainer'>
-            <Button l10nId='copy' className='copyButton whiteButton wideButton' onClick={this.copyToClipboard.bind(this, paymentId)} />
+            <Button l10nId='copy' className='copyButton whiteButton' onClick={this.copyToClipboard.bind(this, paymentId)} />
           </div>
           <div className='keyContainer'>
             <h3 data-l10n-id='firstKey' />
@@ -1097,7 +1097,7 @@ class PaymentsTab extends ImmutableComponent {
         </div>
         <div className='copyKeyContainer'>
           <div className='copyContainer'>
-            <Button l10nId='copy' className='copyButton whiteButton wideButton' onClick={this.copyToClipboard.bind(this, passphrase)} />
+            <Button l10nId='copy' className='copyButton whiteButton' onClick={this.copyToClipboard.bind(this, passphrase)} />
           </div>
           <div className='keyContainer'>
             <h3 data-l10n-id='secondKey' />
@@ -1311,7 +1311,7 @@ class PaymentsTab extends ImmutableComponent {
             <span data-l10n-id='off' />
             <SettingCheckbox dataL10nId='on' prefKey={settings.PAYMENTS_ENABLED} settings={this.props.settings} onChangeSetting={this.props.onChangeSetting} />
           </div>
-          { this.props.ledgerData.get('created') && this.enabled ? <Button l10nId='advancedSettings' className='advancedSettings whiteButton inlineButton wideButton' onClick={this.props.showOverlay.bind(this, 'advancedSettings')} /> : null }
+          { this.props.ledgerData.get('created') && this.enabled ? <Button l10nId='advancedSettings' className='advancedSettings whiteButton' onClick={this.props.showOverlay.bind(this, 'advancedSettings')} /> : null }
         </div>
       </div>
       {