STM32WB: update GCC linker script to match with master

Author: LMESTM

targets/TARGET_STM/TARGET_STM32WB/TARGET_STM32WB55xG/device/TOOLCHAIN_GCC_ARM/stm32wb55xx.ld

@@ -146,6 +146,7 @@ SECTIONS
         __end__ = .;
         end = __end__;
         *(.heap*)
+        . = ORIGIN(RAM1) + LENGTH(RAM1) - STACK_SIZE;
         __HeapLimit = .;
     } > RAM1