Fix tests/test_capabilities.py with correct check of request case

[gschwind]

As far as I know, the OGC standard state that request parameters name such as 'service' or 'request' are not case sensitive, but the values of those are case sensitive [1].

[1] OGC 06-121r3 §11.5.1

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[coveralls]

Coverage remained the same at 81.053% when pulling 89e7a9f on gschwind:service-parameter-is-case-sensitive into 85ca819 on geopython:main.

[cehbrecht]

@gschwind thanks :)