move travis, appveyor, ci.yml.disabled to unmaintained/ (#17828)

* move travis, appveyor, ci.yml.disabled to unmaintained

* update some mentions of travis, appevyor

* fix test

tests/stdlib/tmemlinesBuf.nim

@@ -1,8 +1,3 @@
-discard """
-output: "15"
-disabled: "appveyor"
-"""
-
 import memfiles
 var inp = memfiles.open("tests/stdlib/tmemlinesBuf.nim")
 var buffer: string = ""
@@ -11,5 +6,4 @@ for line in lines(inp, buffer):
   lineCount += 1
 
 close(inp)
-
-echo lineCount
+doAssert lineCount == 9, $lineCount # this file's number of lines

tests/stdlib/tnetdial.nim

@@ -2,7 +2,6 @@ discard """
   cmd: "nim c --threads:on $file"
   exitcode: 0
   output: "OK"
-  disabled: "travis"
 """
 
 import os, net, nativesockets, asyncdispatch