README: Remove incorrect Known Issues section

Issue ARMmbed#40 is closed, ARMmbed#39 is closed as IAR is no longer supported, and
the default applications described have been changed since this issue
was added. These issues are no longer accurate and should be removed.

README.md

@@ -143,13 +143,6 @@ If you don't have a scanner on your phone, please install :
 
 - [ST BLE Profile](https://play.google.com/store/apps/details?id=com.stm.bluetoothlevalidation) for Android.
 
-Known issues
-============
-
-* [NUCLEO_F411RE]: Some BLE examples doesn't work with the ST BLE expansion. See [#40](https://github.com/ARMmbed/mbed-os-example-ble/issues/40)
-* [NRF5] Impossible to debug or flash the examples with IAR: See [#39](https://github.com/ARMmbed/mbed-os-example-ble/issues/39)
-* [NUCLEO_WB55RG]: some examples are not working with default application described in examples readme. Better use [LightBlue](https://itunes.apple.com/gb/app/lightblue-bluetooth-low-energy/id557428110?mt=8) for iPhone or try out [ST BLE Profile](https://play.google.com/store/apps/details?id=com.stm.bluetoothlevalidation).
-
 ### License and contributions
 
 The software is provided under Apache-2.0 license. Contributions to this project are accepted under the same license. Please see contributing.md for more info.