test(std): remove unstable from multiple tests

[trivikr]

$ deno test -A examples/chat/server_test.ts 
Check file:https:///home/trivikr/workspace/deno/std/.deno.test.ts
running 2 tests
test [examples/chat] GET / should serve html ... ok (58ms)
test [examples/chat] GET /ws should upgrade conn to ws ... ok (50ms)

test result: ok. 2 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out (108ms)

$ deno test -A fs/empty_dir_test.ts 
Check file:https:///home/trivikr/workspace/deno/std/.deno.test.ts
running 12 tests
test emptyDirIfItNotExist ... ok (5ms)
test emptyDirSyncIfItNotExist ... ok (2ms)
test emptyDirIfItExist ... ok (3ms)
test emptyDirSyncIfItExist ... ok (3ms)
test [fs] emptyDirPermission test emptyDir("testdata/testfolder") without --allow-read & without --allow-write ... ok (27ms)
test [fs] emptyDirPermission test emptyDirSync("testdata/testfolder") without --allow-read & without --allow-write ... ok (30ms)
test [fs] emptyDirPermission test emptyDir("testdata/testfolder") with --allow-read & without --allow-write ... ok (30ms)
test [fs] emptyDirPermission test emptyDirSync("testdata/testfolder") with --allow-read & without --allow-write ... ok (29ms)
test [fs] emptyDirPermission test emptyDir("testdata/testfolder") without --allow-read & with --allow-write ... ok (30ms)
test [fs] emptyDirPermission test emptyDirSync("testdata/testfolder") without --allow-read & with --allow-write ... ok (32ms)
test [fs] emptyDirPermission test emptyDir("testdata/testfolder") with --allow-read & with --allow-write ... ok (33ms)
test [fs] emptyDirPermission test emptyDirSync("testdata/testfolder") with --allow-read & with --allow-write ... ok (31ms)

test result: ok. 12 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out (255ms)

$ deno test -A fs/exists_test.ts 
Check file:https:///home/trivikr/workspace/deno/std/.deno.test.ts
running 14 tests
test [fs] existsFile ... ok (4ms)
test [fs] existsFileSync ... ok (1ms)
test [fs] existsDirectory ... ok (1ms)
test [fs] existsDirectorySync ... ok (2ms)
test [fs] existsLinkSync ... ok (1ms)
test [fs] existsLink ... ok (1ms)
test [fs] existsPermission test exists("testdata/0.ts") without --allow-read ... Check file:https:///home/trivikr/workspace/deno/std/fs/testdata/exists.ts
ok (457ms)
test [fs] existsPermission test existsSync("testdata/0.ts") without --allow-read ... Check file:https:///home/trivikr/workspace/deno/std/fs/testdata/exists_sync.ts
ok (426ms)
test [fs] existsPermission test exists("testdata/0.ts") with --allow-read ... ok (17ms)
test [fs] existsPermission test existsSync("testdata/0.ts") with --allow-read ... ok (19ms)
test [fs] existsPermission test exists("testdata/no_exist_file_for_test.ts") without --allow-read ... ok (20ms)
test [fs] existsPermission test existsSync("testdata/no_exist_file_for_test.ts") without --allow-read ... ok (20ms)
test [fs] existsPermission test exists("testdata/no_exist_file_for_test.ts") with --allow-read ... ok (19ms)
test [fs] existsPermission test existsSync("testdata/no_exist_file_for_test.ts") with --allow-read ... ok (21ms)

test result: ok. 14 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out (1011ms)

$ deno test -A http/racing_server_test.ts 
Check file:https:///home/trivikr/workspace/deno/std/.deno.test.ts
running 1 tests
test serverPipelineRace ... Check file:https:///home/trivikr/workspace/deno/std/http/racing_server.ts
ok (3993ms)

test result: ok. 1 passed; 0 failed; 0 ignored; 0 measured; 0 filtered out (3993ms) 

cc @lucacasonato

[ry]

LGTM - thanks