[iOS] Fix naming in platform_view example (#144247)

This applies minor cosmetic cleanups noticed while landing fix/tests in another patch. Renames `incrementLabel` to `countLabel` and `setIncrementLabel` to `updateCountLabel`, since it's not setting it to a specific value but rather updating itself based on the current state of the `count` ivar.

No tests since this patch introduces no semantic changes.

Related: https://github.com/flutter/flutter/pull/132028

examples/platform_view/ios/Runner/Base.lproj/Main.storyboard

@@ -129,7 +129,7 @@
                         </constraints>
                     </view>
                     <connections>
-                        <outlet property="incrementLabel" destination="qaB-rs-mWp" id="bFY-of-WoI"/>
+                        <outlet property="countLabel" destination="qaB-rs-mWp" id="bFY-of-WoI"/>
                         <outlet property="incrementButton" destination="6yL-sX-bUL" id="aQR-ap-BrT"/>
                     </connections>
                 </viewController>

examples/platform_view/ios/Runner/PlatformViewController.m

@@ -7,19 +7,19 @@
 #import <Foundation/Foundation.h>
 
 @interface PlatformViewController ()
-@property(weak, nonatomic) IBOutlet UILabel* incrementLabel;
+@property(weak, nonatomic) IBOutlet UILabel* countLabel;
 @end
 
 @implementation PlatformViewController
 
 - (void)viewDidLoad {
   [super viewDidLoad];
-  [self setIncrementLabelText];
+  [self updateCountLabelText];
 }
 
 - (IBAction)handleIncrement:(id)sender {
   self.counter++;
-  [self setIncrementLabelText];
+  [self updateCountLabelText];
 }
 
 - (IBAction)switchToFlutterView:(id)sender {
@@ -27,10 +27,10 @@
   [self dismissViewControllerAnimated:NO completion:nil];
 }
 
-- (void)setIncrementLabelText {
+- (void)updateCountLabelText {
   NSString* text = [NSString stringWithFormat:@"Button tapped %d %@.", self.counter,
                                               (self.counter == 1) ? @"time" : @"times"];
-  self.incrementLabel.text = text;
+  self.countLabel.text = text;
 }
 
 @end