deps: bump nltk to 3.10.3 in longds runner images

[katsugtgz]

Updates nltk in the remaining longds/ runner environment files, following up on #9 which covered the other images.

Evidence:

• the six longds/ files pinned nltk==3.9.3
• osv-scanner reported 64 advisories for nltk@3.9.3, including GHSA-x99w-6fgc-pmfw and GHSA-w3v8-gmh9-3wv7
• updated version: 3.10.3

Validation:

• osv-scanner reports only GHSA-8mgp-746c-j5xp for nltk@3.10.3, which currently has no fixed release (all versions <= 3.10.3 are affected)
• uv pip install nltk==3.10.3 resolves and imports (nltk 3.10.3, requires Python >= 3.10)

Scope: dependency pins in longds/ environment files only.