UI updates

• Add hover state to project stats links (there isn't currently a hover state)
• Fix clone input height (don't know why this keeps breaking)
• Add hover state to top right icons (there isn't currently a hover state)
• Speed up hover transition time (quick fix until https://gitlab.com/gitlab-org/gitlab-ce/issues/26863 is thought out)
• Remove subscribe text from Subscribe button because the button displays only the icon

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