fix: multiple max-height causing multiple instances of scrollbars on attachment modal#994

AnkushBanerjee1999 wants to merge 3 commits intoRocketChat:developRocketChat/EmbeddedChat:developfrom

AnkushBanerjee1999:fix-modal-scrollbarAnkushBanerjee1999/EmbeddedChat:fix-modal-scrollbarCopy head branch name to clipboard