conformance: move the runtime pin to conformance spec 0.2 #113

The CLI's pinned runtime (6f8f73a) predates conformance spec 0.2. As a result, comline conformance can't load a 0.2 corpus (unknown variant handshake_check), so the comline@1 handshake vectors and handshake_check can't be run through --impl.

Found while adding the TypeScript stdio ops server (comline-typescript#104). After this lands:

• comline-typescript bumps VECTORS_REV and adds handshake_check to its ops server;
• the fix for runtime#71 (1 vs 1.0 under compare: json) reaches the CLI with the same bump.