test-console: streamline arrow fn and refine regex

removed unneccessary curly braces and return statement from
inspect arrow function
updated `assert.throws` regex to look for exact match at start
of string

PR-URL: #11039
Reviewed-By: Luigi Pinca <luigipinca@gmail.com>
Reviewed-By: Gibson Fahnestock <gibfahn@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

test/parallel/test-console.js

@@ -22,7 +22,7 @@ assert.doesNotThrow(function() {
 });
 
 // an Object with a custom .inspect() function
-const custom_inspect = { foo: 'bar', inspect: () => { return 'inspect'; } };
+const custom_inspect = { foo: 'bar', inspect: () => 'inspect' };
 
 const stdout_write = global.process.stdout.write;
 const stderr_write = global.process.stderr.write;
@@ -130,7 +130,7 @@ assert.strictEqual(errStrings.length, 0);
 
 assert.throws(() => {
   console.assert(false, 'should throw');
-}, /should throw/);
+}, /^AssertionError: should throw$/);
 
 assert.doesNotThrow(() => {
   console.assert(true, 'this should not throw');