[css-regions-1] Fix spurious / in <img>

[alkorlos]

Fix bikeshed errors.

The command:

bikeshed spec css-regions-1\Overview.bs

Throws errors:

LINE 114:4: Spurious / in <img>.
LINE 122:4: Spurious / in <img>.
LINE 166:4: Spurious / in <img>.
LINE 174:4: Spurious / in <img>.
LINE 1613:3: Spurious / in <img>.
LINE 1677:3: Spurious / in <img>.
LINE 1907:3: Spurious / in <img>.
LINE 1944:3: Spurious / in <img>.
LINE 1976:3: Spurious / in <img>.
LINE 2007:3: Spurious / in <img>.

[w3cbot]

frivoal marked as non substantive for IPR from ash-nazg.