Remove duplicated or unnecessary files

This MR is the primary fix for #4587 (closed). The root cause will be fixed in !24019 (merged).

Duplicated files

• esa_logo_color.svg: !18510 (merged) (@KimLock)
  • cf. !20251 (merged)
  • cc @luke (reviewer)
• jelder.jpg: !23120 (merged) (@jeldergl)
  • cc @sarahod (reviewer)
• saltstack-logo.png: !17260 (merged) (@davistye)
  • cc @dangordon (reviewer)

Unnecessary files

• pdf_gen_stderr.log: !14384 (merged) (@williamchia)
  • Also updates .gitignore

cf. #4587 (closed)