Fix warnings re typedef redefinition in ea7b4e9a2a and 3311ea86ed

Per gripe from Tom Lane and the buildfarm

src/common/jsonapi.c

@@ -78,8 +78,10 @@ typedef enum
  * struct containing the 3 stacks used in non-recursive parsing,
  * and the token and value for scalars that need to be preserved
  * across calls.
+ *
+ * typedef appears in jsonapi.h
  */
-typedef struct JsonParserStack
+struct JsonParserStack
 {
 	int			stack_size;
 	char	   *prediction;
@@ -89,18 +91,20 @@ typedef struct JsonParserStack
 	bool	   *fnull;
 	JsonTokenType scalar_tok;
 	char	   *scalar_val;
-} JsonParserStack;
+};
 
 /*
  * struct containing state used when there is a possible partial token at the
  * end of a json chunk when we are doing incremental parsing.
+ *
+ * typedef appears in jsonapi.h
  */
-typedef struct JsonIncrementalState
+struct JsonIncrementalState
 {
 	bool		is_last_chunk;
 	bool		partial_completed;
 	StringInfoData partial_token;
-} JsonIncrementalState;
+};
 
 /*
  * constants and macros used in the nonrecursive parser

src/common/parse_manifest.c

@@ -91,12 +91,13 @@ typedef struct
 	char	   *manifest_checksum;
 } JsonManifestParseState;
 
-typedef struct JsonManifestParseIncrementalState
+/* typedef appears in parse_manifest.h */
+struct JsonManifestParseIncrementalState
 {
 	JsonLexContext lex;
 	JsonSemAction sem;
 	pg_cryptohash_ctx *manifest_ctx;
-} JsonManifestParseIncrementalState;
+};
 
 static JsonParseErrorType json_manifest_object_start(void *state);
 static JsonParseErrorType json_manifest_object_end(void *state);