Fix wrong calls to `allow_any_instance_of`

Precisely:

  Using `any_instance` to stub a method (secret_variables_for) that has
been defined on a prepended module (EE::Project) is not supported.
Signed-off-by: Rémy Coutable <remy@rymai.me>

spec/models/ci/build_spec.rb

@@ -1694,13 +1694,13 @@ describe Ci::Build do
         allow_any_instance_of(Project)
           .to receive(:predefined_variables) { [project_pre_var] }
 
-        allow_any_instance_of(Project)
+        allow_any_instance_of(EE::Project)
           .to receive(:secret_variables_for)
           .with(ref: 'master', environment: nil) do
             [create(:ci_variable, key: 'secret', value: 'value')]
           end
 
-        allow_any_instance_of(Ci::Pipeline)
+        allow_any_instance_of(EE::Ci::Pipeline)
           .to receive(:predefined_variables) { [pipeline_pre_var] }
       end