Remove unused metar imports

metar.nim

@@ -1,4 +1,4 @@
-import std/[httpclient, os, sequtils, sugar, strutils, xmlparser, xmltree]
+import std/[httpclient, sequtils, sugar, xmlparser, xmltree]
 import strformat
 
 proc getMetar(client: HttpClient, code: string): XMLNode =