chore: add ROUGE and FPR to codespell ignore list

ROUGE is a legitimate ML evaluation metric (Recall-Oriented Understudy
for Gisting Evaluation) used in text summarization benchmarks.

FPR is False Positive Rate, a standard ML classification metric.

.codespell-ignore-words.txt

@@ -31,3 +31,5 @@ panting
 occurence
 socio-economic
 rin
+rouge
+FPR