[AutoMerge] Do not add "blocked" label if already there #1252

Job	Run time
Documentation	1m 44s
Unit/Julia 1.3/ubuntu-latest/x64	8m 57s
Doctests	2m 27s
Unit/Julia 1.4/ubuntu-latest/x64	9m 31s
Unit/Julia 1.5/ubuntu-latest/x64	8m 12s
Unit/Julia 1.6/ubuntu-latest/x64	7m 54s
Unit/Julia 1.7/ubuntu-latest/x64	6m 30s
Unit/Julia 1.8/ubuntu-latest/x64	5m 41s
Unit/Julia 1/ubuntu-latest/x64	6m 53s
Unit/Julia nightly/ubuntu-latest/x64	7m 30s
	1h 5m 19s

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