swap fig1 and fig2 in spark blog

[xiaoshingshing2]

Updated figures in the README to correct references and improve clarity.

Objective of the new blog:
Please describe the intent of the blog.

Signoff section must be completed prior to publishing.

• Technical reviewer approves publishing: (edit and replace with @githubid)
• Editorial team approved publishing: (edit and replace with @githubid)
• Add a thumbnail image for your blog if one is available
• Text nugget summarizing your article. 2-3 lines to draw the reader's attention. Possibly the opening paragraph can be used.
• Blog author team signoffs
  • AMD Employees only: Legal self review traffic lights completed: (edit and replace with @githubid)
  • Licenses file included for content is correct: (edit and replace with @githubid)
  • Changes from technical review and editorial team are acceptable: (edit and replace with @githubid)

[Ehud-Sharlin]

Please merge (edit to an existing blog)