Update Prometheus chart to 10.4.1

We need a chart that will work with K8s versions 1.12 to 1.16. K8s v1.16
removed some deprecated APIs, which causes kube-state-metrics
(a sub-chart of Prometheus) to throw errors (in pod logs).

Prometheus chart v10.4.1 uses kube-state-metrics v1.9.1, which seems to
be compatible with K8s 1.14 to 1.17 (no errors in logs). We are unable
to test compatibility with K8s 1.12/1.13 since these are no longer
available on GKE.

app/models/clusters/applications/prometheus.rb

@@ -5,7 +5,7 @@ module Clusters
     class Prometheus < ApplicationRecord
       include PrometheusAdapter
 
-      VERSION = '9.5.2'
+      VERSION = '10.4.1'
 
       self.table_name = 'clusters_applications_prometheus'
 

changelogs/unreleased/213372-update-prometheus-version.yml

+---
+title: Update Prometheus helm chart version to 10.4.1
+merge_request: 39681
+author:
+type: changed

spec/models/clusters/applications/prometheus_spec.rb

@@ -150,7 +150,7 @@ RSpec.describe Clusters::Applications::Prometheus do
     it 'is initialized with 3 arguments' do
       expect(subject.name).to eq('prometheus')
       expect(subject.chart).to eq('stable/prometheus')
-      expect(subject.version).to eq('9.5.2')
+      expect(subject.version).to eq('10.4.1')
       expect(subject).to be_rbac
       expect(subject.files).to eq(prometheus.files)
     end
@@ -167,7 +167,7 @@ RSpec.describe Clusters::Applications::Prometheus do
       let(:prometheus) { create(:clusters_applications_prometheus, :errored, version: '2.0.0') }
 
       it 'is initialized with the locked version' do
-        expect(subject.version).to eq('9.5.2')
+        expect(subject.version).to eq('10.4.1')
       end
     end
 
@@ -238,7 +238,7 @@ RSpec.describe Clusters::Applications::Prometheus do
     it 'is initialized with 3 arguments' do
       expect(patch_command.name).to eq('prometheus')
       expect(patch_command.chart).to eq('stable/prometheus')
-      expect(patch_command.version).to eq('9.5.2')
+      expect(patch_command.version).to eq('10.4.1')
       expect(patch_command.files).to eq(prometheus.files)
     end
   end