Fix rustdoc errors in components/shared

[Aaryakhandelwal]

1. To fix error in components>shared>embedder>lib.rs: Changed the "unclosed" HTML tag to an inline code using back ticks.
2. To fix error in components>shared>net>request.rs: Added to convert into clickable link.
3. To fix error in components>shared>script>lib.rs: Added closing bracket (>) to fix error.

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• ./mach build -d does not report any errors
• ./mach test-tidy does not report any errors
• These changes are part of Fix as many rustdoc errors as possible #31575
• There are tests for these changes --> Run the command ./mach doc. There shouldn't be any errors/warnings in the above mentioned.

[mrobinson]

Thank you!