MLBEDSW-4576: Update setup.py

This commit changes setup.py to correctly
state that we only officially support Python 3.6.

Signed-off-by: Dwight Lidman <dwight.lidman@arm.com>
Change-Id: Iaa678d1df6a154fdb24f3b3994015a3e842d7696
diff --git a/setup.py b/setup.py
index d43ef16..b2c25ea 100644
--- a/setup.py
+++ b/setup.py
@@ -78,14 +78,13 @@
         "Programming Language :: C",
         "Programming Language :: Python :: 3",
         "Programming Language :: Python :: 3.6",
-        "Programming Language :: Python :: 3.7",
-        "Programming Language :: Python :: 3.8",
+        "Programming Language :: Python :: 3.6 :: Only",
         "Topic :: Scientific/Engineering :: Artificial Intelligence",
         "Topic :: Software Development :: Compilers",
     ],
     keywords=["ethos-u", "vela compiler", "tflite", "npu"],
     packages=find_namespace_packages(include=["ethosu.*"]),
-    python_requires="~=3.6",  # We support only 3.6+
+    python_requires="~=3.6",  # We only test for 3.6.*
     install_requires=[
         "flatbuffers==1.12.0",
         "numpy>=1.16.6",