Fix duplicate flag in makefile (#745)

Author: melissamahoney-mongodb

Makefile

@@ -114,7 +114,7 @@ deploy: build/public
 deploy-search-index:
 	@echo "Building search index"
 	if [ ${STABLE_BRANCH} = ${GIT_BRANCH} ]; then \
-		mut-index upload build/public/${GIT_BRANCH} -o ${PROJECT}-current.json --aliases ${PROJECT}-${GIT_BRANCH} -u ${PRODUCTION_URL}/${PROJECT}/stable -b -b docs-mongodb-org-prd -g -s; \
+		mut-index upload build/public/${GIT_BRANCH} -o ${PROJECT}-current.json --aliases ${PROJECT}-${GIT_BRANCH} -u ${PRODUCTION_URL}/${PROJECT}/stable -b docs-mongodb-org-prd -g -s; \
 	else \
 		mut-index upload build/public/${GIT_BRANCH} -o ${PROJECT}-${GIT_BRANCH}.json -u ${PRODUCTION_URL}/${PROJECT}/${GIT_BRANCH} -b docs-mongodb-org-prd -s; \
 	fi