tests/qapi-schema: Delete two redundant tests

Tests duplicate-key and double-data test the same thing.  The former
predates the latter, and it has a better name.  Delete the latter, and
tweak the former's comment.

Tests include-format-err and include-extra-junk test the same thing.
The former predates the latter, but the latter has a better name and a
comment.  Delete the former.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Message-Id: <20190914153506.2151-3-armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

tests/qapi-schema/double-data.err

@@ -1 +0,0 @@
-tests/qapi-schema/double-data.json:2:41: Duplicate key "data"

tests/qapi-schema/double-data.exit

@@ -1 +0,0 @@
-1

tests/qapi-schema/double-data.json

@@ -1,2 +0,0 @@
-# we reject an expression with duplicate top-level keys
-{ 'struct': 'bar', 'data': { }, 'data': { 'string': 'str'} }

tests/qapi-schema/duplicate-key.json

@@ -1,3 +1,3 @@
-# QAPI cannot include the same key more than once in any {}
+# Cannot include the same key more than once in any {}
 { 'key': 'value',
   'key': 'value' }

tests/qapi-schema/include-format-err.err

@@ -1 +0,0 @@
-tests/qapi-schema/include-format-err.json:1: Invalid 'include' directive

tests/qapi-schema/include-format-err.exit

@@ -1 +0,0 @@
-1

tests/qapi-schema/include-format-err.json

@@ -1,2 +0,0 @@
-{ 'include': 'include-simple-sub.json',
-  'foo': 'bar' }