Drone Security: fix typos

[G1gg1L3s]

Hi! Noticed a couple of typos in the Drone_Security_Cheat_Sheet, so created this PR to fix them.

Additionally, noticed that in the attack vector table, the Security Measures columns are probably flipped:

• Message authentication or digital signature, encrypted traffic/stream are examples of cryptographic measures, but they are in non-cryptographic column
• Traffic filtering, close unused TCP/FTP ports are in cryptographic measures column, but they are examples of non-cryptographic ones

Also, I considered reformatting the table in Markdown (align columns with whitespaces) to make it easier to read, but that would introduce more line changes, so I decided against it. Though, I'm happy to do it if you'd prefer!

• In case of a new Cheat Sheet, you have used the Cheat Sheet template.
• All the markdown files do not raise any validation policy violation, see the policy.
• All the markdown files follow these format rules.
• All your assets are stored in the assets folder.
• All the images used are in the PNG format.
• Any references to websites have been formatted as [TEXT](URL)
• You verified/tested the effectiveness of your contribution (e.g., the defensive code proposed is really an effective remediation? Please verify it works!).
• The CI build of your PR pass, see the build status here.

[szh]

Good catch, thanks for fixing! LGTM

[mackowski]

Thanks @G1gg1L3s