[5032] Fixed some wording and broken unit test

Fixed couple word nits

src/bin/dhcp4/tests/parser_unittest.cc
    void testFile(const std::string& fname) - removed call to
    unlink as it a: doesn't compile on my Mac and b: is not necessary

doc/examples/kea4/advanced.json

@@ -93,7 +93,7 @@
             "pools": [ { "pool": "192.0.4.1 - 192.0.4.254" } ],
             "subnet": "192.0.4.0/24",
 
-            // Sometimes the relay may use an IPv4 address that's not matching
+            // Sometimes the relay may use an IPv4 address that does not match
             // the subnet. This is discouraged, but there are valid cases when it
             // makes sense. One case is when there is a shared subnet.
             "relay": {

src/bin/dhcp4/tests/parser_unittest.cc

@@ -233,8 +233,6 @@ void testFile(const std::string& fname) {
     ASSERT_TRUE(test_json);
 
     compareJSON(reference_json, test_json);
-
-    unlink(decommented);
 }
 
 // This test loads all available existing files. Each config is loaded
@@ -526,7 +524,7 @@ TEST(ParserTest, unicodeEscapes) {
     }
 }
 
-// This test checks that all representations of a slash is recognized properly.
+// This test checks that all representations of a slash are recognized properly.
 TEST(ParserTest, unicodeSlash) {
     // check the 4 possible encodings of solidus '/'
     ConstElementPtr result;