The test class `KeywordFieldMapperTests` contains a switch statement with a branch that will never execute. The test uses a `between(x, y)` switch expression, but the `4` case is outside the randomised range. We need to fix this before #88739 can be merged. By "fix", I mean either remove the spurious case, or if we actually want it then extend the randomized range.
server/src/test/java/org/elasticsearch/index/mapper/KeywordFieldMapperTests.java
public List<SyntheticSourceInvalidExample> invalidExample() throws IOException {
            return List.of(
                new SyntheticSourceInvalidExample(
                    equalTo("field [field] of type [keyword] doesn't support synthetic source because it doesn't have doc values"),
                    b -> b.field("type", "keyword").field("doc_values", false)
                ),
                new SyntheticSourceInvalidExample(
                    equalTo("field [field] of type [keyword] doesn't support synthetic source because it declares ignore_above"),
                    b -> b.field("type", "keyword").field("ignore_above", 10)
                ),
                new SyntheticSourceInvalidExample(
                    equalTo("field [field] of type [keyword] doesn't support synthetic source because it declares a normalizer"),
                    b -> b.field("type", "keyword").field("normalizer", "lowercase")
                )
            );
        }
    }
    @Override
    protected IngestScriptSupport ingestScriptSupport() {
        return new IngestScriptSupport() {
            @Override
            protected StringFieldScript.Factory emptyFieldScript() {
                return (fieldName, params, searchLookup) -> ctx -> new StringFieldScript(fieldName, params, searchLookup, ctx) {
                    @Override
                    public void execute() {}
                };
            }
            @Override
            protected StringFieldScript.Factory nonEmptyFieldScript() {
                return (fieldName, params, searchLookup) -> ctx -> new StringFieldScript(fieldName, params, searchLookup, ctx) {