Update the default issuer in VC JWT tests

[JSAssassin]

The default issuer for the VC JWT tests is set to "SpruceID" which is the only implementor for JWT at the moment

vc-api-verifier-test-suite/tests/11-vc-jwt.js

Lines 44 to 45 in 24de91e

	const issuer = matchingIssuers.get(issuerNameJWT).issuers.find(
	issuer => issuer.tags.has('JWT'));

,

vc-api-verifier-test-suite/tests/test-config.js

Line 6 in 24de91e

export const issuerNameJWT = process.env.ISSUER_NAME_JWT || 'SpruceID';

. We may want to not want to set that to "SpruceID" in future.