Update Secrets Management to Variables and Secrets

We accepted the addition of ~ci::permissions, ~ci::variables, and Deploy Keys/Tokens in !59359 (merged). We received feedback that the name for Secrets Management is misleading since we will be prioritizing variables (and NOT just secrets).

We are changing this category name to Variables and Secrets Management

Approvals

Merge requests with changes to stages and groups and significant changes to categories need to be created, approved, and/or merged by each of the below:

• EVP of Product Management @sfwgitlab
• VP of Product @adawar
• The Product Director relevant to the stage group(s) @kencjohnston @jyavorska
• The Engineering Director relevant to the stage group(s) @dcroft @darbyfrey
• Director of Product Design @vkarnes
• CEO

The following people need to be on the merge request so they stay informed:

• EVP of Engineering @edjdev
• Vice President of Development @clefelhocz1
• Director of Quality @meks
• Vice President of User Experience @clenneville
• The Product Marketing Manager relevant to the stage group(s)