fix typo

Co-authored-by: Charlotte <[email protected]>

backends/cxxrtl/cxxrtl_capi.h

@@ -363,9 +363,9 @@ int64_t cxxrtl_attr_get_signed_int(cxxrtl_attr_set attrs, const char *name);
 // are disabled, returns NULL if the attribute is missing or has an incorrect type.
 const char *cxxrtl_attr_get_string(cxxrtl_attr_set attrs, const char *name);
 
-// Retrieve a string valued attribute from an attribute set.
+// Retrieve a double precision floating point valued attribute from an attribute set.
 //
-// This function asserts that `cxxrtl_attr_type(attrs, name) == CXXRTL_ATTR_STRING`. If assertions
+// This function asserts that `cxxrtl_attr_type(attrs, name) == CXXRTL_ATTR_DOUBLE`. If assertions
 // are disabled, returns NULL if the attribute is missing or has an incorrect type.
 double cxxrtl_attr_get_double(cxxrtl_attr_set attrs, const char *name);