Update macros.

* Remove %_without_hardening_test as f30 was removed from the buildroot.
* Add %test_timeout_scale to improve unstable tests by timeout in ruby.

ruby.yaml

@@ -19,10 +19,9 @@ data:
     dependencies:
         - buildrequires:
             # platform: [] is recommended.
-            # But set "-f28" to avoid the build failure as a temporary workflow.
-            platform: [-f28]
+            platform: [-el8]
           requires:
-            platform: [-f28]
+            platform: [-el8]
     components:
         # SRPMs
         rpms:
@@ -31,8 +30,7 @@ data:
                 rationale: An interpreter of object-oriented scripting language
                 multilib: [x86_64]
                 buildorder: 101
-                # Set a reference on master to guarantee the Ruby version 2.6.
-                ref: 1cc2a49
+                ref: stream-ruby-2.6
             rubygem-abrt:
                 # From rubygem-abrt.spec Summary
                 rationale: >-
@@ -68,6 +66,8 @@ data:
             macros: |
                 # To disable tests in several packages.
                 %_without_tests 1
+                # To avoid the test faiures by timeout in ruby.
+                %test_timeout_scale 6
     api:
         # RPMs
         # From *.spec %package