Fix TypeError in lc addition script post dynamic year being added

[anirudTT]

          this change breaks the scripts when running in GH: 

and causes the following error

    SPDX_DATE = current_year + """Tenstorrent AI ULC
TypeError: unsupported operand type(s) for +: 'int' and 'str'

Originally posted by @anirudTT in #18 (comment)

[anirudTT]

This commit fixes this TypeError in the add_spdx_header.py script where an integer (current_year) was being concatenated with a string without conversion. This caused the workflow to fail when trying to add SPDX license headers to repository files. The issue is now resolved by converting the year to a string before concatenation. This issue may have been introduced here.

@sbennettTT Just bringing this to your attention for your reference. Thank you!

[anirudTT]

Fixed