Change version to 6.0.0.dev0 as 6.0.0-dev0 is incompatiable with the

sanity

Sanity is failing with:
```
ERROR: Found 1 runtime-metadata issue(s) which need to be resolved:
ERROR: meta/runtime.yml:0:0: The tombstone removal_version ('6.0.0') must not be after the current version (SemanticVersion('6.0.0-dev0')) for dictionary value @ data['plugin_routing']['inventory']['k8s']['tombstone']['removal_version']. Got '6.0.0'
```

Versions `6.0.X`, `6.0.0.dev`, and so on considere higther than `6.0.0`
but `6.0.0-dev0` is lower that lead to failing test.

Makefile

@@ -1,5 +1,5 @@
 # Also needs to be updated in galaxy.yml
-VERSION = 6.0.0-dev0
+VERSION = 6.0.0.dev0
 
 TEST_ARGS ?= ""
 PYTHON_VERSION ?= `python -c 'import platform; print(".".join(platform.python_version_tuple()[0:2]))'`

galaxy.yml

@@ -25,7 +25,7 @@ tags:
   - openshift
   - okd
   - cluster
-version: 6.0.0-dev0
+version: 6.0.0.dev0
 build_ignore:
   - .DS_Store
   - "*.tar.gz"