doc: Clean up title case use

doc/src/sgml/appendix-obsolete-default-roles.sgml

@@ -4,7 +4,7 @@
 -->
 
 <sect1 id="default-roles" xreflabel="default-roles">
-  <title>Default Roles renamed to Predefined Roles</title>
+  <title>Default Roles Renamed to Predefined Roles</title>
 
    <indexterm>
      <primary>default-roles</primary>

doc/src/sgml/btree.sgml

@@ -630,7 +630,7 @@ options(<replaceable>relopts</replaceable> <type>local_relopts *</type>) returns
  </sect2>
 
  <sect2 id="btree-deletion">
-  <title>Bottom-up index deletion</title>
+  <title>Bottom-up Index Deletion</title>
   <para>
    B-Tree indexes are not directly aware that under MVCC, there might
    be multiple extant versions of the same logical table row; to an

doc/src/sgml/logicaldecoding.sgml

@@ -1248,7 +1248,7 @@ stream_commit_cb(...);  <-- commit of the streamed transaction
   </sect1>
 
   <sect1 id="logicaldecoding-two-phase-commits">
-   <title>Two-phase commit support for Logical Decoding</title>
+   <title>Two-phase Commit Support for Logical Decoding</title>
 
    <para>
     With the basic output plugin callbacks (eg., <function>begin_cb</function>,