Minor: unnecessary check for specLike on machines running Windows OS

[Nedgeva]

There is a chance forisRoot false negative result due to specific filepath "normalizing" in "json-schema-ref-parser" lib: https://github.com/APIDevTools/json-schema-ref-parser/blob/0980b0a89b7181655129e4e6be7da78dd10d6a4c/lib/util/url.js#L231
So check for root (

swagger-codegen-ts/src/index.ts

Line 50 in a1ef03a

const isRoot = fullPath === spec;

) will fail in some cases:
spec path resolved by node: 'd:\somefolder\somefile'
same path "normalized" by json-schema-ref-parser: 'D:\somefolder\somefile'
See attached pic.