Update cbstats warmup content with bucket data in 7_6

[rao-shwe]

DOC-13324

Preview doc site page for 7.6 version - warmup:

• Removed raw from the command cbstats [host]:[dataport] -b [bucket_name] -p [bucket_password] raw warmup.
• Updated the description of ep_warmup_estimate_time in the table:
  • from "Thne estimated time in microseconds to do warmup."
  • to "The time taken, measured in milliseconds, to discover the estimated number of keys that may be warmed up."
• Corrected ep_warmup_keys_count.
  • Removed s from keys.
• Tested in the 7.6 environment. Added data into the travel-sample bucket, and generated the correct code example request and response.

Preview docs site login credentials.

Ignore the preview yml file.