(core) Swap table and file names in Importer

Summary:
The table name now comes first, making it easier to distinguish
tables coming from an Excel file with multiple sheets.

Test Plan: Tested manually and updated browser test.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3173

app/client/components/Importer.ts

@@ -902,7 +902,7 @@ class CancelledError extends Error {
 
 function getSourceDescription(sourceInfo: SourceInfo, upload: UploadResult) {
   const origName = upload.files[sourceInfo.uploadFileIndex].origName;
-  return sourceInfo.origTableName ? origName + ' - ' + sourceInfo.origTableName : origName;
+  return sourceInfo.origTableName ? `${sourceInfo.origTableName} - ${origName}` : origName;
 }
 
 const cssContainer = styled('div', `