fix: Set min pod spec Swift version to 5.5

Author: cbaker6

ParseSwift.podspec

@@ -14,7 +14,7 @@ Pod::Spec.new do |s|
   s.osx.deployment_target = "10.15"
   s.tvos.deployment_target = "13.0"
   s.watchos.deployment_target = "6.0"
-  s.swift_versions = ['5.3', '5.4', '5.5', '5.6', '5.7']
+  s.swift_versions = ['5.5', '5.6', '5.7']
   s.source_files = "Sources/ParseSwift/**/*.swift"
   s.license = {
     :type => "Apache 2.0",