Fix HZDR Workshop Dates 2021

The Reordering of the GitLab and Python workshops left some confusing information. Update all the events.

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• 03d85f4d - Switch July and August Events

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• 2a8b70f4 - Switch September and October events

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added 1 commit

• b4087dbc - Switch November and December Events

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requested review from @Normo

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• 44bb2833 - Fix error in renaming and switching dates

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• 3b6c960e - Fix metadata was not switch

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added 1 commit

• f6df2c00 - Switched July and August events

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added 2 commits

• dd5a2ff0 - Switched July and August events
• 73f2cbf7 - Removed event that will not take place

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added 2 commits

• 24153bed - Switch September and October events
• 2d088eab - Switch November and December events

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merged

mentioned in commit ef3cef59