ESQL: Fix function registry on windows (#104475)

The registry was replacing LINE_SEPARATOR with " ". But the files
*always* contain `\n`. Never `\r\n`.

Closes #104342

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/expression/function/EsqlFunctionRegistry.java

@@ -264,7 +264,7 @@ public final class EsqlFunctionRegistry extends FunctionRegistry {
         }
         Constructor<?> constructor = constructors[0];
         FunctionInfo functionInfo = constructor.getAnnotation(FunctionInfo.class);
-        String functionDescription = functionInfo == null ? "" : functionInfo.description().replaceAll(System.lineSeparator(), " ");
+        String functionDescription = functionInfo == null ? "" : functionInfo.description().replaceAll("\n", " ");
         String[] returnType = functionInfo == null ? new String[] { "?" } : functionInfo.returnType();
         var params = constructor.getParameters(); // no multiple c'tors supported
 
@@ -277,7 +277,7 @@ public final class EsqlFunctionRegistry extends FunctionRegistry {
                 String name = paramInfo == null ? params[i].getName() : paramInfo.name();
                 variadic |= List.class.isAssignableFrom(params[i].getType());
                 String[] type = paramInfo == null ? new String[] { "?" } : paramInfo.type();
-                String desc = paramInfo == null ? "" : paramInfo.description().replaceAll(System.lineSeparator(), " ");
+                String desc = paramInfo == null ? "" : paramInfo.description().replaceAll("\n", " ");
                 boolean optional = paramInfo == null ? false : paramInfo.optional();
 
                 args.add(new EsqlFunctionRegistry.ArgSignature(name, type, desc, optional));