remove deprecated python virtual environment from Flink/Spark in Jupyter

add flink in jupyter part update spark and flink jupyter notebook

Closes #218 (closed)

requested review from @lazariv--tu-dresden.de

added 2 commits

• 6b296d87 - remove separate flink.md file and move jupyter flink content to big_data_frameworks.md
• fc8e7140 - make linter happy

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added 1 commit

• 897fd9a1 - remove spaces from end of line

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added 1 commit

• 0ac70e38 - Update wordlist.aspell

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added 103 commits

• 0ac70e38...9e9fc537 - 102 commits from branch preview
• 7bad7015 - Merge branch 'preview' into '218-apache-flink'

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mentioned in commit a1ba4d02

merged