go: add «80. Remove Duplicates from Sorted Array II»

URL:	https://leetcode.com/problems/remove-duplicates-from-sorted-array-ii/
Signed-off-by: Matej Focko <me@mfocko.xyz>

go/remove-duplicates-from-sorted-array-ii.go

@@ -0,0 +1,18 @@
+package main
+
+func removeDuplicates(nums []int) int {
+	if len(nums) <= 2 {
+		return len(nums)
+	}
+
+	k := 2
+
+	for i := 2; i < len(nums); i++ {
+		if nums[i] != nums[k-2] {
+			nums[k] = nums[i]
+			k++
+		}
+	}
+
+	return k
+}