fix test suite for new '-d DELIM' tests for node >=12

In node 12 the default Error `toString` changed to include
the stack.

Author: trentm

lib/json.js

@@ -416,7 +416,7 @@ function parseArgv(argv) {
                 parsed.delim = _parseString(outputDelim);
             } catch (parseErr) {
                 throw new Error(format('could not parse delim "%s": %s',
-                    outputDelim, parseErr));
+                    outputDelim, parseErr.message));
             }
             break;
         case '-D':

test/output-delim/expected.stderr

@@ -1,3 +1,3 @@
 # unsupported JavaScript-only escapes in -d DELIM
-json: error: could not parse delim "\0": SyntaxError: Unexpected number in JSON at position 2
-json: error: could not parse delim "\x2c": SyntaxError: Unexpected token x in JSON at position 2
+json: error: could not parse delim "\0": Unexpected number in JSON at position 2
+json: error: could not parse delim "\x2c": Unexpected token x in JSON at position 2