Use uniform naming scheme for TLS 1.3 label structure

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/library/ssl_tls13_keys.h b/library/ssl_tls13_keys.h
index 2b15859..64caa8a 100644
--- a/library/ssl_tls13_keys.h
+++ b/library/ssl_tls13_keys.h
@@ -28,7 +28,7 @@
     MBEDTLS_SSL_TLS1_3_LABEL( finished    , "finished"     )        \
     MBEDTLS_SSL_TLS1_3_LABEL( resumption  , "resumption"   )        \
     MBEDTLS_SSL_TLS1_3_LABEL( traffic_upd , "traffic upd"  )        \
-    MBEDTLS_SSL_TLS1_3_LABEL( export      , "exporter"     )        \
+    MBEDTLS_SSL_TLS1_3_LABEL( exporter    , "exporter"     )        \
     MBEDTLS_SSL_TLS1_3_LABEL( key         , "key"          )        \
     MBEDTLS_SSL_TLS1_3_LABEL( iv          , "iv"           )        \
     MBEDTLS_SSL_TLS1_3_LABEL( sn          , "sn"           )        \