Prevent tests from detecting our fake tzdata package

Tests from test_zoneinfo assume that if `tzdata` package is installed,
it provides standalone timezone data.  Our `tzdata` package is just
a shim, so force falsify that assumption.

Signed-off-by: Michał Górny <mgorny@gentoo.org>

Lib/test/test_zoneinfo/test_zoneinfo.py

@@ -24,11 +24,8 @@
 lzma = import_module('lzma')
 py_zoneinfo, c_zoneinfo = test_support.get_modules()
 
-try:
-    importlib.metadata.metadata("tzdata")
-    HAS_TZDATA_PKG = True
-except importlib.metadata.PackageNotFoundError:
-    HAS_TZDATA_PKG = False
+# Gentoo installs a dummy `tzdata` package
+HAS_TZDATA_PKG = False
 
 ZONEINFO_DATA = None
 ZONEINFO_DATA_V1 = None