Fix some grammar errors in bloom.sgml

Discussion: https://postgr.es/m/CAEepm%3D3sijpGr8tXdyz-7EJJZfhQHABPKEQ29gpnb7-XSy%2B%3D5A%40mail.gmail.com
Reported-by: Thomas Munro
Backpatch-through: 9.6

doc/src/sgml/bloom.sgml

@@ -51,9 +51,9 @@
     <term><literal>length</literal></term>
     <listitem>
      <para>
-      Length of each signature (index entry) in bits, it is rounded up to the
+      Length of each signature (index entry) in bits. It is rounded up to the
       nearest multiple of <literal>16</literal>. The default is
-      <literal>80</literal> bits and maximum is <literal>4096</literal>.
+      <literal>80</literal> bits and the maximum is <literal>4096</literal>.
      </para>
     </listitem>
    </varlistentry>