Fix podspec warning

Author: echo-branch

Branch.podspec

@@ -14,7 +14,7 @@ Use the Branch SDK (branch.io) to create and power the links that point back to
   s.homepage         = "https://help.branch.io/developers-hub/docs/ios-sdk-overview"
   s.license          = 'MIT'
   s.author           = { "Branch" => "[email protected]" }
-  s.source           = { git: "https://github.com/BranchMetrics/ios-branch-deep-linking-attribution", tag: s.version.to_s }
+  s.source           = { git: "https://github.com/BranchMetrics/ios-branch-deep-linking-attribution.git", tag: s.version.to_s }
   s.ios.deployment_target = '9.0'
   s.tvos.deployment_target = '9.0'