Reduce noise when running spec/lib/gdk/command/open_spec.rb

What does this merge request do and why?

This MR fixes noisy output when running spec/lib/gdk/command/open_spec.rb:

Before

$ be rspec spec/lib/gdk/command/open_spec.rb
.Opening http://127.0.0.1:3000
checking for xdg-open... no
checking for gp... no
..Opening http://127.0.0.1:3000
checking for xdg-open... no
checking for gp... no
.Opening http://127.0.0.1:3000
checking for xdg-open... no
checking for gp... no
.Opening http://127.0.0.1:3000
checking for xdg-open... no
checking for gp... no
.Opening http://127.0.0.1:3000
.

Finished in 0.0594 seconds (files took 0.2987 seconds to load)
7 examples, 0 failures

After

$ be rspec spec/lib/gdk/command/open_spec.rb
.......

Finished in 0.0705 seconds (files took 0.29214 seconds to load)
7 examples, 0 failures

cc @abitrolly

Impacted categories

The following categories relate to this merge request:

• gdk-reliability - e.g. When a GDK action fails to complete.
• gdk-usability - e.g. Improvements or suggestions around how the GDK functions.
• gdk-performance - e.g. When a GDK action is slow or times out.

Merge request checklist

• This change is backward compatible. If not, please include steps to communicate to our users.
• Tests added for new functionality. If not, please raise an issue to follow-up.
• Documentation added/updated, if needed.
• Announcement added, if change is notable.
• gdk doctor test added, if needed.
• Add the ~highlight label if this MR should be included in the CHANGELOG.md.

Related #1997 (closed)