Fix lots of spelling errors (#7751)

* Fix a typo

* Fix lots of spelling errors

* Fix a few more spelling mistakes

* s/parsable/parseable/

* Don't touch the third party files

* Cloneable is the preferred C# term

* Copyable is the preferred C++ term

* Revert "s/parsable/parseable/"

This reverts commit 534ecf7675222f39d98928c7e1489b56b004b774.

* Revert unparseable->unparsable corrections
diff --git a/php/tests/descriptors_test.php b/php/tests/descriptors_test.php
index 60a6292..b2c5e01 100644
--- a/php/tests/descriptors_test.php
+++ b/php/tests/descriptors_test.php
@@ -108,7 +108,7 @@
 
     public function testEnumDescriptor()
     {
-        // WARNINIG - we need to do this so that TestDescriptorsEnum is registered!!?
+        // WARNING - we need to do this so that TestDescriptorsEnum is registered!!?
         new TestDescriptorsMessage();
 
         $pool = DescriptorPool::getGeneratedPool();