Replace generic exception with ValueError in linear search

[anureetkaur55]

Description

Replaced the generic Exception with ValueError in rec_linear_search() for more specific and Pythonic error handling.

Also improved the docstring wording for better readability.

Changes Made

• Replaced Exception with ValueError
• Improved docstring description

Type of Change

• Code quality improvement

• Documentation improvement

• Add an algorithm?

• Fix a bug or typo in an existing algorithm?

• Add or change doctests? -- Note: Please avoid changing both code and tests in a single pull request.

• Documentation change?

Checklist:

• I have read CONTRIBUTING.md.
• This pull request is all my own work -- I have not plagiarized.
• I know that pull requests will not be merged if they fail the automated tests.
• This PR only changes one algorithm file. To ease review, please open separate PRs for separate algorithms.
• All new Python files are placed inside an existing directory.
• All filenames are in all lowercase characters with no spaces or dashes.
• All functions and variable names follow Python naming conventions.
• All function parameters and return values are annotated with Python type hints.
• All functions have doctests that pass the automated testing.
• All new algorithms include at least one URL that points to Wikipedia or another similar explanation.
• If this pull request resolves one or more open issues then the description above includes the issue number(s) with a closing keyword: "Fixes #ISSUE-NUMBER".