[item] Fix Drowned Research Codex description during rework #49

Summary

Track the Drowned Research Codex tooltip grammar fix until the planned codex rework in a future PR.

Required change

In blighted-smp/src/main/java/fr/moussax/blightedSMP/content/items/materials/FishingMaterials.java, update the DROWNED_RESEARCH_CODEX description. The current text reads “A preserved collection of research behind by an unknown explorer.” Add the missing verb so it reads “A preserved collection of research left behind by an unknown explorer.” If the rework replaces this description, ensure the replacement is grammatically complete.

Rationale

Players see this description in the item tooltip. The current sentence is missing a verb. This temporary follow-up defers the change from PR #48 to the planned codex rework.

Acceptance criteria

• The Drowned Research Codex tooltip contains a grammatically complete description.
• Preserve the surrounding description unless the codex rework intentionally replaces it.
• Check the rendered tooltip for readability.

Context

Requested by @Trixmas.

• PR: refactor: items engine modernization #48
• Review thread: refactor: items engine modernization #48 (comment)