Fix thread column showing pin button (#11891)

Fix #11467

app/javascript/mastodon/components/column_header.js

@@ -120,7 +120,7 @@ class ColumnHeader extends React.PureComponent {
           <button title={formatMessage(messages.moveRight)} aria-label={formatMessage(messages.moveRight)} className='text-btn column-header__setting-btn' onClick={this.handleMoveRight}><Icon id='chevron-right' /></button>
         </div>
       );
-    } else if (multiColumn) {
+    } else if (multiColumn && this.props.onPin) {
       pinButton = <button key='pin-button' className='text-btn column-header__setting-btn' onClick={this.handlePin}><Icon id='plus' /> <FormattedMessage id='column_header.pin' defaultMessage='Pin' /></button>;
     }
 
@@ -142,7 +142,7 @@ class ColumnHeader extends React.PureComponent {
       collapsedContent.push(pinButton);
     }
 
-    if (children || multiColumn) {
+    if (children || (multiColumn && this.props.onPin)) {
       collapseButton = <button className={collapsibleButtonClassName} title={formatMessage(collapsed ? messages.show : messages.hide)} aria-label={formatMessage(collapsed ? messages.show : messages.hide)} aria-pressed={collapsed ? 'false' : 'true'} onClick={this.handleToggleClick}><Icon id='sliders' /></button>;
     }