[iOS] Bump up the cocoapods version (pytorch#49176)

Summary:
Pull Request resolved: pytorch#49176

Bump up the cocoapods version
ghstack-source-id: 118305636

Test Plan: CI

Reviewed By: xta0

Differential Revision: D25466321

fbshipit-source-id: 916adc514c5edc8971445da893362a160cfc092b

Author: husthyc

ios/LibTorch.podspec

@@ -1,6 +1,6 @@
 Pod::Spec.new do |s|
     s.name             = 'LibTorch'
-    s.version          = '1.7.0'
+    s.version          = '1.7.1'
     s.authors          = 'PyTorch Team'
     s.license          = { :type => 'BSD' }
     s.homepage         = 'https://github.com/pytorch/pytorch'