Update library/contextvars.po

Co-authored-by: Dr.XYZ <dr.xyz.tw@gmail.com>

Author: husohome

library/contextvars.po

@@ -358,7 +358,7 @@ msgstr ""
 "\n"
 "def main():\n"
 "    # 'var' 之前被設成 'spam'\n"
-"    # 呼叫 'copy_context()' 和 'ctx.run(main)'，所以:\n"
+"    # 呼叫 'copy_context()' 和 'ctx.run(main)'，所以：\n"
 "    print(var.get())  # 'spam'\n"
 "    print(ctx[var])  # 'spam'\n"
 "\n"