EDCK: don't serialize default values

[albertmink]

Example contains default values that are specified in JSON Schema. As per specification of the ABAP file formats, this is not needed and shall be removed.

Example

abap-file-formats/file-formats/edck/examples/z_aff_example_edck.edck.json

Lines 9 to 11 in 06134bd

	"checkCategory": "existenceCheck",
	"checkClassification": "coreDeliveredChecks",
	"resultProcessDerived": false

with defaults as and others

abap-file-formats/file-formats/edck/edck-v1.json

Line 84 in 06134bd

"default": "existenceCheck"

Please @KUMARMUKULSAP clean the example accordingly (for some reason I cannot assign you directly to the issue).