activity_pub_controller.ex: fix typo

7 jobs for features/apc2s-media-upload-object in 9 minutes and 53 seconds (queued for 3 seconds)
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passed #67541
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00:01:35

 
  Test
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analysis

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passed #67544
lint

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passed #67542
unit-testing

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87.4%
passed #67543
unit-testing-rum

00:08:17

 
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manual #67546
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manual #67547
allowed to fail manual
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