Update the run logic of iOS jobs (#2118)

Summary:
This PR updates the logic when these iOS jobs should be run. This change just makes it run for pushes to iOS folders and xplat c++ folders.

## Changelog

- Update the GH action.

Pull Request resolved: https://github.com/facebook/flipper/pull/2118

Test Plan: Note that no iOS job is run.

Reviewed By: mweststrate

Differential Revision: D27395681

Pulled By: priteshrnandgaonkar

fbshipit-source-id: 37a7c2fb9b3fdfa22307ac5e7403364bfeb0a384

.github/workflows/iOS-Sample.yml

@@ -1,5 +1,14 @@
 name: Build iOS apps
-on: [push, pull_request]
+on:
+  push:
+    paths:
+      - "iOS/**"
+      - "xplat/**"
+  pull_request:
+    paths:
+      - "iOS/**"
+      - "xplat/**"
+
 jobs:
   build-sample-objc:
     runs-on: macos-latest

.github/workflows/iOS-pod-lint.yml

@@ -1,5 +1,13 @@
 name: Validate Podspecs
-on: [push, pull_request]
+on:
+  push:
+    paths:
+      - "iOS/**"
+      - "xplat/**"
+  pull_request:
+    paths:
+      - "iOS/**"
+      - "xplat/**"
 
 jobs:
   lint-flipperkit_pod: