Update ApplicationSetting npm_package_requests_forwarding default

What does this MR do?

A new ApplicationSetting has been introduced with !25346 (merged): npm_package_requests_forwarding. The column definition has been set to default: false.

According to https://about.gitlab.com/handbook/product/#principles, the setting should be set to default: true. See the following comment: #55344 (comment 291909539)

This MR:

• updates the npm_package_requests_forwarding column definition so that default: true.
• updates existing rows (which is a single one) so that the npm_package_requests_forwarding value is set to true.

This MR is part of the work for this issue: #55344 (closed). As such, there is no documentation or changelog for this MR. They will added in a future MR.

The complete feature is gated behind a feature flag. See !25531 (merged).

Database

Here is the log of the migration running:

$ rails db:migrate
== 20200221105436 UpdateApplicationSettingNpmPackageRequestsForwardingDefault: migrating 
-- change_column_default(:application_settings, :npm_package_requests_forwarding, true)
   -> 0.0266s
-- execute("UPDATE application_settings SET npm_package_requests_forwarding = TRUE")
   -> 0.0042s
== 20200221105436 UpdateApplicationSettingNpmPackageRequestsForwardingDefault: migrated (0.0309s) 

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team

Closes #55344 (closed)