Gemfile: update rbpdf version to 1.18.1 (#17570)

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remove trailing white-space from app/models/issue_custom_field.rb

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4013410
Add a constraint on "shoulda-matchers" version (#17828).

This helps bundler find its dependencies in case shoulda-matchers v1.4.2 is
already installed. In such a case bundler breaks while it shouldn't.

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4013411
Expire other sessions on password change (#17796).

Contributed by Jan Schulz-Hofen.

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extra : convert_revision : svn%3Ae93f8b46-1217-0410-a6f0-8f06a7374b81/trunk%4013412