[hca] Use fedora:rawhide now that greenlet 0.4.16 is released

In Change-Id: Ice75ae880925cd15c096eb6d1cdabf7f802bccde, we pinned
fedora:32 but now that greenlet 0.4.16 is released with support for
Python 3.9, we can unpin this.

Story: 2007264
Task: 39967

Change-Id: I841c78a942e87a25ef6ae04b24a1f7c73c48f096

dockerfiles/heat-container-agent/Dockerfile

@@ -1,4 +1,4 @@
-FROM fedora:32
+FROM fedora:rawhide
 
 ARG ARCH=x86_64