Rollup PR for docs

[0xc0170]

Description

PR:

• Fix typos in RTOS doxygen. #8623
• Fix typos in Events doxygen #8622
• Typo fixes in Doxygen for Platform #8617
• Doxy fix on netsocket docs #8603

Pull request type

[X] Fix
[ ] Refactor
[ ] Target update
[ ] Functionality change
[ ] Docs update
[ ] Test update
[ ] Breaking change

[0xc0170]

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 3558
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/8652/

Triggering tests

/morph test
/morph export-build
/morph mbed2-build

[mbed-ci]

Exporter Build : SUCCESS

Build number : 3166
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/8652/

[mbed-ci]

Test : SUCCESS

Build number : 3340
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/8652/3340