Update FirebaseSessions.podspec

Co-authored-by: Nick Cooke <36927374+ncooke3@users.noreply.github.com>

Author: samedson

FirebaseSessions.podspec

@@ -32,10 +32,7 @@ Pod::Spec.new do |s|
   s.cocoapods_version = '>= 1.4.0'
   s.prefix_header_file = false
 
-  base_dir = "FirebaseSessions/Sources/"
-  s.source_files = [
-    base_dir + '**/*.swift',
-  ]
+  s.source_files = "FirebaseSessions/Sources/**/*.swift"
 
   s.dependency 'FirebaseCore', '~> 10.0'
   s.dependency 'FirebaseCoreExtension', '~> 10.0'