Update iOS examples page

[TheDauntless]

The main trigger was the syntax blocks on ios/examples but modified some additional things while I was fixing it.

ios/examples.md

• Converted ios examples to syntax highlighting blocks
• Added a bit of context at the top
• Moved away from the list-based structure as that clashes with the syntax blocks
• Removed frida-cli specific info from ios examples page, as this explanation is already present in frida-cli / frida-trace and not ios specific

frida-cli.md

• Removed header output from frida-cli examples. This is more in-line with other examples now

frida-trace.md

• Updated frida-trace -h output