Placeholder updates

[trevorld]

• [x] Move "beard" and "beardbw" service URLs from "http" to "https"
• [x] Remove "cage" and "cagebw"? service currently not working
• ~Contact "kitten" service about newish buggy behaviour?~
• [x] Remove "lorempixel" and "lorempixelbw"? service currently not working
• [x] Remove "murray" and "murraybw"? service currently not working
• [x] Remove "placeimg" and "placeimgbw" - service documented as ending in July 2023
• [x] Update relevant {ggpattern} vignette

[trevorld]

• "cage" has an alternative provider: https://placecage.lucidinternets.com/
• "murray" has an alternative provider: https://fillmurray.lucidinternets.com/
• "seagal" has an alternative provider: https://stevensegallery.lucidinternets.com/