Rename 1929-concatenation-of-array to 1929-concatenation-of-array.go

[Resolved PR Comment] Added .go extension to file name

Author: Sar-Go

Diff for: go/1929-concatenation-of-array renamed to go/1929-concatenation-of-array.go

@@ -10,4 +10,4 @@ func getConcatenation(nums []int) []int {
 	}
 
 	return ans
-}
+}