cinder/docs directory has a references to the Dell EMC company name.
Rename all Dell EMC references to Dell, except for those references where there are paths.
When the user will read the documentation he will see the new company name.
These changes are due to the company’s rebranding.
Closes-Bug: #1970208
Change-Id: I60e06b1b42974ce7ef4d790f050d706dc1a8a7a3