Confidential icon mis-alignment in issue header

Summary

When viewing a confidential issue the icon at the top of the page near the issues title is slightly mis-aligned

Steps to reproduce

View any confidential issue and look at the icon at the top of the page

Example Project

https://gitlab.com/gitlab-org/gitlab/-/issues/240880

Relevant logs and/or screenshots

Possible fixes

The icon SVG has an incorrect vertical-align: text-bottom style applied to it inherited from .issuable-warning-icon .icon. Simply removing the vertical-align property re-aligns the icon correctly within the box.