Changes in examples: change Pandas on Polars

[alinzh]

[pep8speaks]

Hello @alinzh! Thanks for opening this PR. We checked the lines you've touched for PEP 8 issues, and found:

• In the file kickoff/miner_bgkmeans.py:

Line 30:80: E501 line too long (92 > 79 characters) Line 58:80: E501 line too long (84 > 79 characters) Line 59:14: W292 no newline at end of file

• In the file kickoff/miner_propstruct.py:

Line 24:80: E501 line too long (90 > 79 characters) Line 37:80: E501 line too long (99 > 79 characters) Line 47:80: E501 line too long (102 > 79 characters) Line 76:80: E501 line too long (88 > 79 characters) Line 89:80: E501 line too long (81 > 79 characters) Line 93:80: E501 line too long (82 > 79 characters) Line 95:80: E501 line too long (85 > 79 characters)

[alinzh]

@blokhin can we merge it?