Fix strawberry versions (#474)

Author: TimPansino

tox.ini

@@ -301,7 +301,8 @@ deps =
     framework_starlette-starlette0014: starlette<0.15
     framework_starlette-starlette0015: starlette<0.16
     framework_starlette-starlettelatest: starlette
-    framework_strawberry: starlette
+    ; Strawberry 0.95.0 is incompatible with Starlette 0.18.0, downgrade until future release
+    framework_strawberry: starlette<0.18.0
     framework_strawberry-strawberrylatest: strawberry-graphql
     framework_tornado: pycurl
     framework_tornado-tornado0600: tornado<6.1