Change directory from 'license' to 'licenses' for runtime-swift

[mrutkows]

The runtime-swift binary-release archive of project licenses is under directory named 'license' (singular), but the convention is to use the directory name 'licenses' (plural). Here is the directory that contains the folder that should be renamed to be plural:
https://github.com/apache/incubator-openwhisk-release/tree/master/archive/convenience-binaries/openwhisk-runtime-swift

This was originally reported in this issue apache/openwhisk-runtime-swift#52
in the runtime-swift repo. which I will close.

[houshengbo]

@mrutkows This issue is fixed.