Fix a couple typos in BRIN code

Typos introduced by commits c1ec02be1d, b437571714 and dae761a87e.

Author: Alvaro Herrera
Reported-by: Alexander Lakhin
Discussion: https://postgr.es/m/202401091043.e3nrqiad6gb7@alvherre.pgsql

doc/src/sgml/indexam.sgml

@@ -370,7 +370,7 @@ aminsert (Relation indexRelation,
    initially). After the index insertions complete, the memory will be freed
    automatically. If additional cleanup is required (e.g. if the cache contains
    buffers and tuple descriptors), the AM may define an optional function
-   <literal>indexinsertcleanup</literal>, called before the memory is released.
+   <literal>aminsertcleanup</literal>, called before the memory is released.
   </para>
 
   <para>

src/backend/access/brin/brin.c

@@ -222,7 +222,7 @@ static bool add_values_to_range(Relation idxRel, BrinDesc *bdesc,
 								BrinMemTuple *dtup, const Datum *values, const bool *nulls);
 static bool check_null_keys(BrinValues *bval, ScanKey *nullkeys, int nnullkeys);
 static void brin_fill_empty_ranges(BrinBuildState *state,
-								   BlockNumber prevRange, BlockNumber maxRange);
+								   BlockNumber prevRange, BlockNumber nextRange);
 
 /* parallel index builds */
 static void _brin_begin_parallel(BrinBuildState *buildstate, Relation heap, Relation index,
@@ -1151,8 +1151,8 @@ brinbuild(Relation heap, Relation index, IndexInfo *indexInfo)
 	 *
 	 * XXX plan_create_index_workers makes the number of workers dependent on
 	 * maintenance_work_mem, requiring 32MB for each worker. That makes sense
-	 * for btree, but not for BRIN, which can do away with much less memory.
-	 * So maybe make that somehow less strict, optionally?
+	 * for btree, but not for BRIN, which can do with much less memory. So
+	 * maybe make that somehow less strict, optionally?
 	 */
 	if (indexInfo->ii_ParallelWorkers > 0)
 		_brin_begin_parallel(state, heap, index, indexInfo->ii_Concurrent,
@@ -2621,7 +2621,7 @@ _brin_parallel_merge(BrinBuildState *state)
 
 	/*
 	 * Initialize BrinMemTuple we'll use to union summaries from workers (in
-	 * case they happened to produce parts of the same paga range).
+	 * case they happened to produce parts of the same page range).
 	 */
 	memtuple = brin_new_memtuple(state->bs_bdesc);
 
@@ -2932,7 +2932,7 @@ _brin_parallel_build_main(dsm_segment *seg, shm_toc *toc)
  * specified block number. The empty tuple is initialized only once, when it's
  * needed for the first time, stored in the memory context bs_context to ensure
  * proper life span, and reused on following calls. All empty tuples are
- * exactly the same except for the bs_blkno field, which is set to the value
+ * exactly the same except for the bt_blkno field, which is set to the value
  * in blkno parameter.
  */
 static void