doc: Improve description of min_dynamic_shared_memory

While on it, fix one oversight in 90fbf7c5, that introduced a reference
to an incorrect value for the compression level of pg_dump.

Author: Justin Pryzby
Reviewed-by: Thomas Munro, Michael Paquier
Discussion: https://postgr.es/m/CA+hUKGJRTLWWPcQfjm_xaOk98M8aROK903X92O0x-4vLJPWrrA@mail.gmail.com

doc/src/sgml/config.sgml

@@ -1939,13 +1939,13 @@ include_dir 'conf.d'
       <listitem>
        <para>
         Specifies the amount of memory that should be allocated at server
-        startup time for use by parallel queries.  When this memory region is
+        startup for use by parallel queries.  When this memory region is
         insufficient or exhausted by concurrent queries, new parallel queries
         try to allocate extra shared memory temporarily from the operating
         system using the method configured with
         <varname>dynamic_shared_memory_type</varname>, which may be slower due
         to memory management overheads.  Memory that is allocated at startup
-        time with <varname>min_dynamic_shared_memory</varname> is affected by
+        with <varname>min_dynamic_shared_memory</varname> is affected by
         the <varname>huge_pages</varname> setting on operating systems where
         that is supported, and may be more likely to benefit from larger pages
         on operating systems where that is managed automatically.

src/bin/pg_dump/pg_backup_archiver.h

@@ -332,7 +332,6 @@ struct _archiveHandle
 	int			compression;	/*---------
 								 * Compression requested on open().
 								 * Possible values for compression:
-								 * -2	ZSTD_COMPRESSION
 								 * -1	Z_DEFAULT_COMPRESSION
 								 *  0	COMPRESSION_NONE
 								 * 1-9 levels for gzip compression