I am using the following htaccess rul to remove double or more slashes from web urls:
#remove double/more slashes in url RewriteCond %{REQUEST_URI} ^(.*)//(.
Give it a try with:
RewriteCond %{THE_REQUEST} ^[A-Z]{3,}\s/{2,} [NC] RewriteRule ^(.*) $1 [R=301,L]
It should redirect to a single slash at the end of the domain. And an improvement on yours:
RewriteCond %{REQUEST_URI} ^(.*)/{2,}(.*)$ RewriteRule . %1/%2 [R=301,L]