Update clause_specification_text.adoc

Corrected my mental glitch, thank you @kschleidt

Author: chris-little

standard/clause_specification_text.adoc

@@ -283,7 +283,7 @@ where `"SST_mean"` references the following parameter:
       "en": "Sea surface temperature daily mean"
     },
 "statisticalMeasure": "https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Arithmetic_mean",
-"narrower": "http://www.w3.org/2004/02/skos/core"
+"narrower": ["http://vocab.nerc.ac.uk/standard_name/sea_surface_temperature/"]
   },
   "unit" : {
     "label": {
@@ -308,7 +308,7 @@ and `"SST_stddev"` references the following parameter:
       "en": "Sea surface temperature standard deviation of daily mean"
     },
 "statisticalMeasure": "https://ec.europa.eu/eurostat/statistics-explained/index.php?title=Glossary:Standard_deviation",
-"narrower": "http://www.w3.org/2004/02/skos/core"
+"narrower": ["http://vocab.nerc.ac.uk/standard_name/sea_surface_temperature/"]
   },
   "unit" : {
     "label": {