travis: exclude one file from scanning licenses
travis: exclude one file from scanning licenses

tools/test/toolchains/api_test.py is problematic as it contains code
for checking tools. This contains license code in strings - scancode things these are the licenses in the file.

We skip it checking in travis

kjbracey-arm/mbed,kjbracey-arm/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,kjbracey-arm/mbed,mbedmicro/mbed,mbedmicro/mbed,mbedmicro/mbed