Fix assorted doc typos

Erik Rijkers and Justin Pryzby

Backpatch to v14

Discussion: https://www.postgresql.org/message-id/b79bfeff-d0e3-29a3-2576-0e325848dede%40xs4all.nl

Author: j-naylor

doc/src/sgml/brin.sgml

@@ -75,7 +75,7 @@
    summarized will cause the summary information to be updated with data
    from the new tuples.
    When a new page is created that does not fall within the last
-   summarized range, the range that the new page belongs into
+   summarized range, the range that the new page belongs to
    does not automatically acquire a summary tuple;
    those tuples remain unsummarized until a summarization run is
    invoked later, creating the initial summary for that range.

doc/src/sgml/ref/drop_extension.sgml

@@ -81,8 +81,8 @@ DROP EXTENSION [ IF EXISTS ] <replaceable class="parameter">name</replaceable> [
     <listitem>
      <para>
       This option prevents the specified extensions from being dropped
-      if there exists non-extension-member objects that depends on any
-      the extensions.  This is the default.
+      if there exist non-extension-member objects that depend on any
+      of the extensions.  This is the default.
      </para>
     </listitem>
    </varlistentry>