Remove use of deprecated tar.TypeRegA

Fixes golangci-lint message:

`tar.TypeRegA has been deprecated since Go 1.11 and an alternative has
been available since Go 1.1: Use TypeReg instead.`

Signed-off-by: Chris Evich <cevich@redhat.com>

copier/copier.go

@@ -1721,7 +1721,7 @@ func copierHandlerPut(bulkReader io.Reader, req request, idMappings *idtools.IDM
 			// no type flag for sockets
 			default:
 				return fmt.Errorf("unrecognized Typeflag %c", hdr.Typeflag)
-			case tar.TypeReg, tar.TypeRegA:
+			case tar.TypeReg:
 				var written int64
 				written, err = createFile(path, tr)
 				// only check the length if there wasn't an error, which we'll

copier/copier_test.go

@@ -710,7 +710,7 @@ func testStat(t *testing.T) {
 								result := st.Results[glob]
 
 								switch testItem.Typeflag {
-								case tar.TypeReg, tar.TypeRegA:
+								case tar.TypeReg:
 									if actualContent, ok := testArchive.contents[testItem.Name]; ok {
 										testItem.Size = int64(len(actualContent))
 									}