PR template: fix target update list

[0xc0170]

Description

Not only new target, any target update goes to own section. This covers
target updates to SDK, HAL implementation, target list, etc.
All these go to patch releases.

what about Feature - this is for features, but also shall cover new functionality (is this clear enough that even adding new function to public API this makes it "feature"?) ?

Pull request type

[X] Fix
[ ] Refactor
[ ] Target update
[ ] Feature
[ ] Breaking change

[NirSonnenschein]

@0xc0170 does this need CI? (I've put the label on since it seems to be approved on review, but I'm not sure if this needs an actual CI run)

[0xc0170]

@0xc0170 does this need CI? (I've put the label on since it seems to be approved on review, but I'm not sure if this needs an actual CI run)

Yes please. Will start one

/morph build

[mbed-ci]

Build : SUCCESS

Build number : 2735
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/7689/

Triggering tests

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

[mbed-ci]

Exporter Build : SUCCESS

Build number : 2369
Build artifacts/logs : http://mbed-os.s3-website-eu-west-1.amazonaws.com/?prefix=builds/exporter/7689/

[mbed-ci]

Test : SUCCESS

Build number : 2462
Test logs :http://mbed-os-logs.s3-website-us-west-1.amazonaws.com/?prefix=logs/7689/2462

[0xc0170]

/morph mbed2-build