Maintain supported sanic version range

Author: WilliamBergamin

requirements/adapter.txt

@@ -15,7 +15,7 @@ Werkzeug>=2,<4
 pyramid>=1,<3
 sanic>=20,<21; python_version=="3.6"
 sanic>=21,<24; python_version>"3.6" and python_version<="3.8"
-sanic>=24,<25; python_version>"3.8"
+sanic>=21,<25; python_version>"3.8"
 starlette>=0.14,<1
 tornado>=6,<7
 uvicorn<1                                # The oldest version can vary among Python runtime versions