test_fluentd: Fix failed tests on Ruby 3.3 #1247

Job	Run time
Unit testing with Ruby 3.3 on macos-latest	21m 1s
Unit testing with Ruby 3.3 on macos-latest	21m 1s
Unit testing with Ruby 3.3 on macos-latest	21m 1s
Unit testing with Ruby 3.3 on macos-latest	21m 1s
Unit testing with Ruby 3.3 on macos-latest	21m 1s
Unit testing with Ruby 3.2 on macos-latest	19m 45s
Unit testing with Ruby 3.2 on macos-latest	18m 57s
Unit testing with Ruby 3.2 on macos-latest	19m 22s
Unit testing with Ruby 3.2 on macos-latest	19m 32s
Unit testing with Ruby 3.2 on macos-latest	19m 6s
Unit testing with Ruby 3.1 on macos-latest	19m 34s
Unit testing with Ruby 3.1 on macos-latest	19m 34s
Unit testing with Ruby 3.1 on macos-latest	19m 34s
Unit testing with Ruby 3.1 on macos-latest	19m 34s
Unit testing with Ruby 3.1 on macos-latest	19m 34s
Unit testing with Ruby 3.0 on macos-latest	19m 0s
Unit testing with Ruby 3.0 on macos-latest	19m 0s
Unit testing with Ruby 3.0 on macos-latest	19m 0s
Unit testing with Ruby 3.0 on macos-latest	19m 0s
Unit testing with Ruby 3.0 on macos-latest	19m 0s
Unit testing with Ruby 2.7 on macos-latest	20m 3s
Unit testing with Ruby 2.7 on macos-latest	20m 3s
Unit testing with Ruby 2.7 on macos-latest	20m 3s
Unit testing with Ruby 2.7 on macos-latest	20m 3s
Unit testing with Ruby 2.7 on macos-latest	20m 3s
Unit testing with Ruby head on macos-latest	22m 23s
Unit testing with Ruby head on macos-latest	22m 23s
Unit testing with Ruby head on macos-latest	22m 23s
Unit testing with Ruby head on macos-latest	22m 23s
Unit testing with Ruby head on macos-latest	22m 23s
	10h 6m 47s

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