Fixed get_code_region_around_line() boundary issue

[mou23]

In the get_code_region_around_line() function, line_no is 1-based, so we need to ensure that the last valid line is included in the output.
If line_no + window_size exceeds len(file_content), the current implementation excludes the last line due to the exclusive nature of range(start, end).
To fix this issue, I added 1 to len(file_content), ensuring that the last line is included.

Additionally, i in range(start, end) is 1-based because start and end are derived from line_no, which follows 1-based indexing.
Without adjusting the index in the else block, using file_content[i] would be off by one, potentially leading to an IndexError or retrieving the wrong lines.
To fix this, I replaced file_content[i] with file_content[i - 1]