remove raja related docs

remove raja related pages since there is no active raja development at NERSC.

This MR will solve the ticket #298 (closed).

After this MR, if one search raja, one will only see raja keywords in e4s project description.

wwei@DOE7632155 nersc.gitlab.io % grep -irl raja *
docs/applications/e4s/spack.md

Submitters and reviewers please make sure

• [x ] internal links are relative and to the .md file
• [x ] avoid links named "here"
• [x ] alt-text for images is descriptive
• [x ] doesn't duplicate existing content
• [x ] spell check
• [x ] renders correctly
• [x ] does not include any identifiable information (real usernames, project names, etc)