In docs, change a few cases of "not important" to "unimportant".

doc/src/sgml/advanced.sgml

@@ -173,7 +173,7 @@ UPDATE branches SET balance = balance + 100.00
    </para>
 
    <para>
-    The details of these commands are not important here; the important
+    The details of these commands are unimportant here; the important
     point is that there are several separate updates involved to accomplish
     this rather simple operation.  Our bank's officers will want to be
     assured that either all these updates happen, or none of them happen.
@@ -428,7 +428,7 @@ SELECT depname, empno, salary, rank() OVER (PARTITION BY depname ORDER BY salary
 
    <para>
     We already saw that <literal>ORDER BY</> can be omitted if the ordering
-    of rows is not important.  It is also possible to omit <literal>PARTITION
+    of rows is unimportant.  It is also possible to omit <literal>PARTITION
     BY</>, in which case there is just one partition containing all the rows.
    </para>
 

doc/src/sgml/ltree.sgml

@@ -160,7 +160,7 @@ Europe & Russia*@ & !Transportation
      This will match paths that contain the label <literal>Europe</literal> and
      any label beginning with <literal>Russia</literal> (case-insensitive),
      but not paths containing the label <literal>Transportation</literal>.
-     The location of these words within the path is not important.
+     The location of these words within the path is unimportant.
      Also, when <literal>%</> is used, the word can be matched to any
      underscore-separated word within a label, regardless of position.
     </para>

doc/src/sgml/syntax.sgml

@@ -2361,7 +2361,7 @@ LANGUAGE SQL IMMUTABLE STRICT;
     <literal>b</literal> inputs will be concatenated, and forced to either
     upper or lower case depending on the <literal>uppercase</literal>
     parameter.  The remaining details of this function
-    definition are not important here (see <xref linkend="extend"> for
+    definition are unimportant here (see <xref linkend="extend"> for
     more information).
    </para>
 

doc/src/sgml/tablefunc.sgml

@@ -516,7 +516,7 @@ row_name   extra   cat1   cat2   cat3   cat4
     In practice the <parameter>source_sql</parameter> query should always
     specify <literal>ORDER BY 1</> to ensure that values with the same
     <structfield>row_name</structfield> are brought together.  However,
-    ordering of the categories within a group is not important.
+    ordering of the categories within a group is unimportant.
     Also, it is essential to be sure that the order of the
     <parameter>category_sql</parameter> query's output matches the specified
     output column order.