[gardening] add spaces after commas, for readability

Author: glessard

stdlib/public/core/Sequence.swift

@@ -1140,24 +1140,24 @@ extension Sequence {
   @inlinable
   public __consuming func _copyContents(
     initializing buffer: UnsafeMutableBufferPointer<Element>
-  ) -> (Iterator,UnsafeMutableBufferPointer<Element>.Index) {
+  ) -> (Iterator, UnsafeMutableBufferPointer<Element>.Index) {
     return _copySequenceContents(initializing: buffer)
   }
 
   @_alwaysEmitIntoClient
   internal __consuming func _copySequenceContents(
     initializing buffer: UnsafeMutableBufferPointer<Element>
-  ) -> (Iterator,UnsafeMutableBufferPointer<Element>.Index) {
+  ) -> (Iterator, UnsafeMutableBufferPointer<Element>.Index) {
     var it = self.makeIterator()
-    guard var ptr = buffer.baseAddress else { return (it,buffer.startIndex) }
+    guard var ptr = buffer.baseAddress else { return (it, buffer.startIndex) }
     for idx in buffer.startIndex..<buffer.count {
       guard let x = it.next() else {
         return (it, idx)
       }
       ptr.initialize(to: x)
       ptr += 1
     }
-    return (it,buffer.endIndex)
+    return (it, buffer.endIndex)
   }
 
   @inlinable