Add whitespace to description

Per NASA-PDS/pds4-information-model#744 (comment), this is a workaround to bug in LDDTool

src/PDS4_VGR_IngestLDD.xml

@@ -289,7 +289,7 @@
     <submitter_name>Matthew Tiscareno</submitter_name>
     <definition>Optical filter used for the image.
     This attribute corresponds to the keyword FILTER_NAME in earlier versions of Voyager data products.
-    For details see the documentation at https://pds-rings.seti.org/voyager/iss/inst_cat_na1.html and https://pds-rings.seti.org/voyager/iss/inst_cat_wa1.html</definition>
+    For details see the documentation at https://pds-rings.seti.org/voyager/iss/inst_cat_na1.html and https://pds-rings.seti.org/voyager/iss/inst_cat_wa1.html </definition>
     <DD_Value_Domain>
       <enumeration_flag>true</enumeration_flag>
       <value_data_type>ASCII_Short_String_Collapsed</value_data_type>