There is currently no pre-existing option to disable floats in the script language, but you can easily do that with a minor customization to the library by finding and disabling the tokens that represents the floats.
The file as_tokendef.h holds the definitions of the tokens that the script language understands. You'll want to disable the tokens ttFloatConstant, ttDoubleConstant, ttFloat, and ttDouble. Doing that and then compiling the library you'll easily find where they are referred from and can disable the code that uses those too.
Another option, that might be even simpler, is to change the method asCBuilder::CreateDataTypeFromNode to give an error if the script attempts to declare any variables of the types float or double. That combined with the fact that you'll not register any application interface that accepts floats will effectively disable the use of floats in the scripts without a lot of changes in the library code.
I may even consider adding the latter as a dynamic option through an engine property.