doc: fix spelling "connction" to "connection"

Was wrong in commit 1a9388bd.

Reported-by: Tom Lane, Justin Pryzby

Discussion: https://postgr.es/m/20201102063333.GE22691@telsasoft.com

Backpatch-through: 9.5

doc/src/sgml/ref/pg_basebackup.sgml

@@ -654,7 +654,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Specifies parameters used to connect to the server, as a <link
-        linkend="libpq-connstring">connction string</link>;  these
+        linkend="libpq-connstring">connection string</link>;  these
         will override any conflicting command line options.
        </para>
        <para>

doc/src/sgml/ref/pg_dumpall.sgml

@@ -550,7 +550,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Specifies parameters used to connect to the server, as a <link
-        linkend="libpq-connstring">connction string</link>;  these
+        linkend="libpq-connstring">connection string</link>;  these
         will override any conflicting command line options.
        </para>
        <para>

doc/src/sgml/ref/pg_receivewal.sgml

@@ -253,7 +253,7 @@ PostgreSQL documentation
       <listitem>
        <para>
         Specifies parameters used to connect to the server, as a <link
-        linkend="libpq-connstring">connction string</link>;  these
+        linkend="libpq-connstring">connection string</link>;  these
         will override any conflicting command line options.
        </para>
        <para>