Rename spree:install to solidus:install in the sandbox template

[blocknotes]

spree:install task have been renamed to solidus:install (reference https://github.com/solidusio/solidus/pull/3538)

We had an issue while creating new sandboxes with solidus_subscriptions extension (ref: https://github.com/solidusio-contrib/solidus_subscriptions/issues/196).

Tests

• I uninstalled previous versions of solidus_dev_support from my system
• I installed solidus_dev_support from this PR branch
• I executed solidus extension . in solidus_dev_support project to update bin/sandbox
• I recreated the sandbox using bin/rails-sandbox

Result:

• The "Could not find generator 'spree:install'." error line is gone

Checklist

• [X] I have structured the commits for clarity and conciseness.
• [ ] I have added relevant automated tests for this change.

[mergify[bot]]

It looks like this PR is missing a label to determine the type of change it introduces. The maintainer should add one of the following labels:

• bug for bugfixes.
• enhancement for new features and improvements.
• documentation for documentation changes.
• security for security patches.
• removed for feature removals.
• infrastructure for internal changes that should not go in the changelog.

Additionally, the maintainer may also want to add one of the following:

• breaking for breaking changes.
• deprecated for feature deprecations.

Once the correct labels have been set, simply remove the needs changelog label label from this PR so I can merge it.