email: fix typo

app/views/notify/new_issue_email.text.erb

@@ -2,4 +2,4 @@ New Issue was created.
 
 Issue <%= @issue.iid %>: <%= url_for(namespace_project_issue_url(@issue.project.namespace, @issue.project, @issue)) %>
 Author:    <%= @issue.author_name %>
-Asignee:  <%= @issue.assignee_name %>
+Assignee:  <%= @issue.assignee_name %>

app/views/notify/new_merge_request_email.text.erb

@@ -4,5 +4,5 @@ New Merge Request #<%= @merge_request.iid %>
 
 <%= merge_path_description(@merge_request, 'to') %>
 Author:    <%= @merge_request.author_name %>
-Asignee:  <%= @merge_request.assignee_name %>
+Assignee:  <%= @merge_request.assignee_name %>