fix: jypytext not found and update vim health methods

[gogamid]

Fix: jypytext not available on macOS Sonoma 14.5

Problem: jypytext was not found on macOS Sonoma 14.5 using global package, virtual environment, or Python host via vim.g.

Solution: Using a table in vim.fn.system instead of a string fixes the issue.

Changes:

• Changed string to table in vim.fn.system.
• Additionally updated vim.health methods.

[gogamid]

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