chore(tier2): drop unused gitignore entries

The scripts/tier2/state/ and scripts/tier2/failures/ entries were
added when those were the default locations. After Tier 2's
project-relative relocation (commit 923d360d), the actual defaults
are tests/artifacts/tier2_state/ and tests/artifacts/tier2_failures/,
which are already covered by the existing tests/artifacts/ entry.

The scripts/tier2/state/ and scripts/tier2/failures/ dirs are no
longer created by anything, so the gitignore entries were dead
config.

Refs: conductor/tracks/tier2_no_appdata_20260618 (post-merge followup)

.gitignore

@@ -9,8 +9,6 @@ credentials.toml
 uv.lock
 md_gen
 scripts/generated
-scripts/tier2/state/
-scripts/tier2/failures/
 logs
 logs/sessions/
 logs/agents/