Remove genpinmap as moved to the STM32 core

Refers to stm32duino/Arduino_Core_STM32#1091

Signed-off-by: Frederic Pillon <frederic.pillon@st.com>

Author: fpistm

README.md

@@ -2,4 +2,4 @@
 [![GitHub release](https://img.shields.io/github/release/stm32duino/Arduino_Tools.svg)](https://github.com/stm32duino/Arduino_Tools/releases/latest)
 [![GitHub commits](https://img.shields.io/github/commits-since/stm32duino/Arduino_Tools/1.4.0.svg)](https://github.com/stm32duino/Arduino_Tools/compare/1.4.0...master)
 
-Contains upload tools for STM32 based boards and some other usefull scripts (ex: [genpinmap](https://github.com/stm32duino/Arduino_Tools/tree/master/src/genpinmap))
+Contains upload tools for STM32 based boards and some other usefull scripts.