[unittest] remove unnecessay export for testing (#20868)

lib/pure/unittest.nim

@@ -433,8 +433,6 @@ proc matchFilter(suiteName, testName, filter: string): bool =
   return glob(suiteName, suiteAndTestFilters[0]) and
          glob(testName, suiteAndTestFilters[1])
 
-when defined(testing): export matchFilter
-
 proc shouldRun(currentSuiteName, testName: string): bool =
   ## Check if a test should be run by matching suiteName and testName against
   ## test filters.

tests/stdlib/tunittest.nim

@@ -23,6 +23,7 @@ targets: "c js"
 """
 
 import std/[unittest, sequtils, assertions]
+from std/unittest {.all.} import matchFilter
 
 proc doThings(spuds: var int): int =
   spuds = 24