fix: correct bumpFactor divisor to match number of checks (CM-1137)

There are 6 metadata checks in decideMemberSimilarityUsingAdditionalChecks
but the divisor was 5 — each bump was slightly too large and the sixth
check was mathematically unreachable before hitting the Math.min(1) cap.

Co-Authored-By: Claude Sonnet 4.6 <noreply@anthropic.com>

Author: skwowet

services/apps/merge_suggestions_worker/src/memberSimilarityCalculator.ts

@@ -472,7 +472,7 @@ class MemberSimilarityCalculator {
         ? startingScore
         : this.HIGH_CONFIDENCE_SCORE
 
-    const bumpFactor = (1 - confidenceScore) / 5
+    const bumpFactor = (1 - confidenceScore) / 6
 
     if (this.hasSameLocation(member, similarMember)) {
       isHighConfidence = true