Fix test collection errors: SyntaxError and NameError in various files

[ArnavGarg7]

This PR fixes multiple bugs that were preventing pytest from properly collecting and running tests due to SyntaxError and NameError exceptions during the import/collection phase.

Changes made
maths/matrix_exponentiation.py: Fixed a NameError where Matrix was referenced in its own class methods as a type hint before it was fully defined. Resolved this by adding from future import annotations.
web_programming/fetch_well_rx_price.py: Fixed a SyntaxError: multiple exception types must be parenthesized. The code was using Python 2 exception syntax (except httpx.HTTPError, ValueError:). Updated it to the correct Python 3 syntax (except (httpx.HTTPError, ValueError):).
web_programming/instagram_crawler.py: Fixed an identical SyntaxError for multiple exception types (except json.decoder.JSONDecodeError, KeyError:). Updated it to except (json.decoder.JSONDecodeError, KeyError):.
Testing
Ran pytest locally on the affected files to ensure they can now be imported and collected without throwing fatal syntax or name errors.

[algorithms-keeper]

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