Prometheus exporter: stop converting 1 to ratio

[jack-berg]

To reflect this (likely) spec change: https://github.com/open-telemetry/opentelemetry-specification/pull/4966/changes#r3011432569

opentelemetry-java/exporters/prometheus/src/main/java/io/opentelemetry/exporter/prometheus/PrometheusUnitsHelper.java

Line 56 in 9b602eb

initUnit("1", "ratio");