Logging test reveals differences between mac and windows

[hustf]

It seems PR #165 did not fully fix logging tests.

This on Julia version 1.5.3. Tests pass locally on max and on CI, but:

Default metadata formatting: Test Failed at C:\Users\F\.julia\dev\WebSockets\test\test_websocketlogger.jl:59
  Expression: Logging.default_metafmt(Error, Main, :g, :i, "", 0) == (:light_red, "Error:", "@ Main :0")
   Evaluated: (:yellow, "Error:", "@ Main :0") == (:light_red, "Error:", "@ Main :0")
Stacktrace:
 [1] top-level scope at C:\Users\F\.julia\dev\WebSockets\test\test_websocketlogger.jl:59
 [2] top-level scope at C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\Test\src\Test.jl:1115
 [3] top-level scope at C:\Users\F\.julia\dev\WebSockets\test\test_websocketlogger.jl:53
 [4] top-level scope at C:\buildbot\worker\package_win64\build\usr\share\julia\stdlib\v1.5\Test\src\Test.jl:1115
 [5] top-level scope at C:\Users\F\.julia\dev\WebSockets\test\test_websocketlogger.jl:18

......

Test Summary:                              | Pass  Fail  Total
WebSockets                                 | 1040     1   1041
  Base.show                                |   33           33
  WebSocketLogger                          |   56     1     57
    WebSocketLogger                        |   35     1     36
      Default metadata formatting          |    8     1      9
      Prefix and suffix layout             |    4            4
      Metadata suffix, right justification |    7            7
      Limiting large data structures       |    2            2
    WebSocketLogger_special                |   21           21
  Fragment and unit                        |  823          823
  Handshake                                |   27           27
  Client                                   |   13           13
  Client_listen                            |   18           18
  Client_serverWS                          |   20           20
  Abrupt close & error handling            |   50           50
ERROR: LoadError: Some tests did not pass: 1040 passed, 1 failed, 0 errored, 0 broken.