Update PYPI_PACKAGE to lowercase since that's what the upstream tarball
now uses.

ptest results:

|============================================================================
|Testsuite summary
|# TOTAL: 500
|# PASS: 447
|# SKIP: 53
|# XFAIL: 0
|# FAIL: 0
|# XPASS: 0
|# ERROR: 0
|DURATION: 2
|END: /usr/lib/python3-mako/ptest
|2024-10-22T17:30
|STOP: ptest-runner
|TOTAL: 1 FAIL: 0

Changelog (https://docs.makotemplates.org/en/latest/changelog.html

):

-   Fixed long standing bug where the sequence <& would be
    misinterpreted by the lexer. It’s not clear why the ampersand
    character was part of the characters being consumed here and it may
    have been an inadvertent bit of code from one of Mako’s predecessor
    languages.

    References: #412

(From OE-Core rev: 3871ceb5927d4540e0a109d47d5a08a12a0d48a5)

Signed-off-by: Trevor Gamblin <tgamblin@baylibre.com>
Signed-off-by: Richard Purdie <richard.purdie@linuxfoundation.org>