Revert "python-requirements.txt: Bump the supported version of meson"

This reverts commit 54da889ea56ce4e23182e4c42561bbeb6b0cd26a because it
causes all SW unit tests to be skipped in CI and freshly built
containers.

Fixes #6794

Signed-off-by: Alphan Ulusoy <alphan@google.com>
diff --git a/python-requirements.txt b/python-requirements.txt
index e46bc76..4eee2a4 100644
--- a/python-requirements.txt
+++ b/python-requirements.txt
@@ -13,7 +13,7 @@
 libcst
 livereload
 mako
-meson >= 0.53.0, <= 0.56 # minimum matches version in meson.build
+meson >= 0.53.0, <= 0.54 # minimum matches version in meson.build
 mistletoe>=0.7.2
 mypy
 # Premailer 3.9.0 broke the API by introducing an allow_loading_external_files