build: avoid ".* suffix ..." error with the latest pip

It looks like the support for the deprecated syntax
was completely removed in pip 24.1.
See https://discuss.python.org/t/should-we-permit-with-more-comparision-operators-in-version-specifiers/22782.

requirements.txt

@@ -1,2 +1,2 @@
 # optional
-Pygments>=2.11.2,<=2.16.* # 2.11.2 is the last version which supports the old Python 3.5
+Pygments>=2.11.2,<=2.16 # 2.11.2 is the last version which supports the old Python 3.5