fixes nim-lang#22519; DocGen does not work for std/times on JS backend (nim-lang#22738)

fixes nim-lang#22519

Author: ringabout

lib/pure/times.nim

@@ -2787,7 +2787,9 @@ proc epochTime*(): float {.tags: [TimeEffect].} =
   ##
   ## .. warning:: Unsuitable for benchmarking (but still better than `now`),
   ##    use `monotimes.getMonoTime` or `cpuTime` instead, depending on the use case.
-  when defined(macosx):
+  when defined(js):
+    result = newDate().getTime() / 1000
+  elif defined(macosx):
     var a {.noinit.}: Timeval
     gettimeofday(a)
     result = toBiggestFloat(a.tv_sec.int64) + toBiggestFloat(
@@ -2804,8 +2806,6 @@ proc epochTime*(): float {.tags: [TimeEffect].} =
     var secs = i64 div rateDiff
     var subsecs = i64 mod rateDiff
     result = toFloat(int(secs)) + toFloat(int(subsecs)) * 0.0000001
-  elif defined(js):
-    result = newDate().getTime() / 1000
   else:
     {.error: "unknown OS".}