[Docs] Add type double to apiFilesSyntax.dox
[Docs] Add type double to apiFilesSyntax.dox

Change-Id: Iec5f9399fa05bd3dfcb42b2e495764d25bb5c648
Resolves: LE-5679

legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af,legatoproject/legato-af