[ios] Fix font for ClearBrowsingDataTableView Button

UIButton's don't handle dynamic types well. So we'll keep it fixed at a bold 17px.

Screenshots: https://drive.google.com/file/d/1befS0btYrluxxdfjZ-RJJ4aUnluyylX8/view?usp=sharing
https://drive.google.com/file/d/1tQSYQrDqmWuWhNVmJkYxjHy9Yp75OZ9L/view?usp=sharing

Bug: 865008

Change-Id: Ic76e8264123b647cfe19e580e1abdd98b9e6a229
Reviewed-on: https://chromium-review.googlesource.com/1145227
Commit-Queue: Chris Lu <[email protected]>
Reviewed-by: Sergio Collazos <[email protected]>
Cr-Original-Commit-Position: refs/heads/master@{#576929}(cherry picked from commit 2a982a1)
Reviewed-on: https://chromium-review.googlesource.com/1148614
Cr-Commit-Position: refs/branch-heads/3497@{#56}
Cr-Branched-From: 271eaf5-refs/heads/master@{#576753}

ios/chrome/browser/ui/table_view/cells/table_view_text_button_item.mm

@@ -28,6 +28,8 @@
 const CGFloat buttonTitleVerticalContentInset = 8.0;
 // Button corner radius.
 const CGFloat buttonCornerRadius = 8;
+// Font Size for Button Title Label.
+const CGFloat buttonTitleFontSize = 17.0;
 }  // namespace
 
 @implementation TableViewTextButtonItem
@@ -83,7 +85,7 @@ - (instancetype)initWithStyle:(UITableViewCellStyle)style
                       forState:UIControlStateNormal];
     self.button.translatesAutoresizingMaskIntoConstraints = NO;
     [self.button.titleLabel
-        setFont:[UIFont preferredFontForTextStyle:UIFontTextStyleHeadline]];
+        setFont:[UIFont boldSystemFontOfSize:buttonTitleFontSize]];
     self.button.layer.cornerRadius = buttonCornerRadius;
     self.button.clipsToBounds = YES;
     self.button.contentEdgeInsets = UIEdgeInsetsMake(