Fix missing template apply button in Redmine 6.0

[hidakatsuya]

In Redmine 6.0, the template apply button is not displayed, making it unclickable.

This issue occurs because the display style for elements with the .icon class has changed to inline-flex in Redmine 6.0.
https://github.com/redmine/redmine/blob/0abf7105dab7c6558a26cdcc28c6770ad89649d0/app/assets/stylesheets/application.css#L1728
This change affects all icon-only elements in this plugin.

To resolve this, I modified to replace the .icon class with the existing .icon-only class for all icon elements.

I verified all icon-only images display correctly.

Results for other pages

Note (the template in the 2nd line is a global note template):

Add global template/note form:

Plugin configuration form:

Environments:

Environment:
  Redmine version                6.0.0.stable
  Ruby version                   3.3.4-p94 (2024-07-09) [x86_64-linux]
  Rails version                  7.2.2
  Environment                    development
  Database adapter               SQLite
  Mailer queue                   ActiveJob::QueueAdapters::AsyncAdapter
  Mailer delivery                smtp
Redmine settings:
  Redmine theme                  Default
SCM:
  Subversion                     1.14.2
  Mercurial                      6.3.2
  Cvs                            1.12.13
  Bazaar                         3.3.2
  Git                            2.39.2
  Filesystem                     
Redmine plugins:
  redmine_issue_templates        1.2.1

[hidakatsuya]

I also verified that it displays correctly in Redmine 5.1.

Issue Template:

Template for note:

Environment:
  Redmine version                5.1.3.stable
  Ruby version                   3.2.4-p170 (2024-04-23) [x86_64-linux]
  Rails version                  6.1.7.8
  Environment                    development
  Database adapter               SQLite
  Mailer queue                   ActiveJob::QueueAdapters::AsyncAdapter
  Mailer delivery                smtp
Redmine settings:
  Redmine theme                  Bleuclair
SCM:
  Subversion                     1.14.2
  Mercurial                      6.3.2
  Cvs                            1.12.13
  Bazaar                         3.3.2
  Git                            2.39.2
  Filesystem                     
Redmine plugins:
  redmine_issue_templates        1.2.1