Use host URL to build JIRA remote link icon

app/models/project_services/jira_service.rb

 class JiraService < IssueTrackerService
   include Gitlab::Routing
+  include ApplicationHelper
+  include ActionView::Helpers::AssetUrlHelper
 
   validates :url, url: true, presence: true, if: :activated?
   validates :api_url, url: true, allow_blank: true
@@ -268,7 +270,9 @@ class JiraService < IssueTrackerService
         url: url,
         title: title,
         status: status,
-        icon: { title: 'GitLab', url16x16: 'https://gitlab.com/favicon.ico' }
+        icon: {
+          title: 'GitLab', url16x16: asset_url('favicon.ico', host: gitlab_config.url)
+        }
       }
     }
   end

changelogs/unreleased/issue_31081.yml

+---
+title: Use host URL to build JIRA remote link icon
+merge_request:
+author:
+type: other

spec/models/project_services/jira_service_spec.rb

@@ -166,7 +166,6 @@ describe JiraService do
 
       # Creates comment
       expect(WebMock).to have_requested(:post, @comment_url)
-
       # Creates Remote Link in JIRA issue fields
       expect(WebMock).to have_requested(:post, @remote_link_url).with(
         body: hash_including(
@@ -174,7 +173,7 @@ describe JiraService do
           object: {
             url: "#{Gitlab.config.gitlab.url}/#{project.full_path}/commit/#{merge_request.diff_head_sha}",
             title: "GitLab: Solved by commit #{merge_request.diff_head_sha}.",
-            icon: { title: "GitLab", url16x16: "https://gitlab.com/favicon.ico" },
+            icon: { title: "GitLab", url16x16: "http://localhost/favicon.ico" },
             status: { resolved: true }
           }
         )

spec/services/system_note_service_spec.rb

@@ -789,7 +789,7 @@ describe SystemNoteService do
               object: {
                 url: project_commit_url(project, commit),
                 title: "GitLab: Mentioned on commit - #{commit.title}",
-                icon: { title: "GitLab", url16x16: "https://gitlab.com/favicon.ico" },
+                icon: { title: "GitLab", url16x16: "http://localhost/favicon.ico" },
                 status: { resolved: false }
               }
             )
@@ -815,7 +815,7 @@ describe SystemNoteService do
               object: {
                 url: project_issue_url(project, issue),
                 title: "GitLab: Mentioned on issue - #{issue.title}",
-                icon: { title: "GitLab", url16x16: "https://gitlab.com/favicon.ico" },
+                icon: { title: "GitLab", url16x16: "http://localhost/favicon.ico" },
                 status: { resolved: false }
               }
             )
@@ -841,7 +841,7 @@ describe SystemNoteService do
               object: {
                 url: project_snippet_url(project, snippet),
                 title: "GitLab: Mentioned on snippet - #{snippet.title}",
-                icon: { title: "GitLab", url16x16: "https://gitlab.com/favicon.ico" },
+                icon: { title: "GitLab", url16x16: "http://localhost/favicon.ico" },
                 status: { resolved: false }
               }
             )