Fix the labal of the article

content/post/cache-unfriendly.md

@@ -1,7 +1,7 @@
 +++
 date = 2018-08-01T18:50:00+08:00
 draft = false
-tags = ["cache", "xdoj-next"]
+tags = ["cache", "XDOJ-next"]
 title = "Cache Unfriendly Program and Judging Issues"
 summary = """
 Some problems and solutions have caused strange behavior of XDOJ judging