Basic test case: copr build only

This test case is triggered automatically by our validation script.

```yaml
- job: copr_build
  trigger: pull_request
  targets:
  - fedora-all
```

Author: lbarcziova

.packit.yaml

@@ -14,8 +14,7 @@ jobs:
 - job: copr_build
   trigger: pull_request
   targets:
-  - fedora-stable-x86_64
-  - fedora-rawhide-x86_64
+  - fedora-all
 
 - job: copr_build
   trigger: release
@@ -28,12 +27,6 @@ jobs:
   targets:
     - fedora-stable
 
-- job: tests
-  trigger: pull_request
-  targets:
-  - fedora-stable-x86_64
-  - fedora-rawhide-x86_64
-
 - job: propose_downstream
   trigger: release
   packit_instances: ["stg"]