Fix error message for interval_coverage_quantile()

[nikosbosse]

Description

The previous version had a typo:

1: In (function (observed, predicted, quantile, range = 50)  :
  To compute the interval coverage for a range of 50%, the quantiles 0.250.75 are required. Returning `NA`.

This PR fixes this so that the message now reads:

1: In (function (observed, predicted, quantile, range = 50)  :
  To compute the interval coverage for a range of 50%, the quantiles `0.25, 0.75` are required. Returning `NA`.

Checklist

• My PR is based on a package issue and I have explicitly linked it.
• I have included the target issue or issues in the PR title as follows: issue-number: PR title
• I have tested my changes locally.
• I have added or updated unit tests where necessary.
• I have updated the documentation if required.
• I have built the package locally and run rebuilt docs using roxygen2.
• My code follows the established coding standards and I have run lintr::lint_package() to check for style issues introduced by my changes.
• I have added a news item linked to this PR.
• I have reviewed CI checks for this PR and addressed them as far as I am able.

[codecov]

Codecov Report

Attention: 2 lines in your changes are missing coverage. Please review.

Comparison is base (2ff165f) 83.71% compared to head (a88369c) 83.66%.

Files	Patch %	Lines
R/metrics-quantile.R	0.00%	2 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff             @@
##           develop     #549      +/-   ##
===========================================
- Coverage    83.71%   83.66%   -0.05%     
===========================================
  Files           21       21              
  Lines         1719     1720       +1     
===========================================
  Hits          1439     1439              
- Misses         280      281       +1     

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[seabbs]

Ha I was just looking at this in the testing update.