internals: document when "hello" and "capabilities" commands were added

Both were introduced in 0.9.1.

"hello" made its entrance in b17eebc911ae, 144280f1578f, and
a1cfe679192c to support SSH.

"capabilities" was added in c660691fb45d to support HTTP.

Differential Revision: https://phab.mercurial-scm.org/D2000

mercurial/help/internals/wireprotocol.txt

@@ -662,6 +662,8 b' There is no trailing newline.'
 
 This command does not accept any arguments. Return type is a ``string``.
 
+This command was introduced in Mercurial 0.9.1 (released July 2006).
+
 changegroup
 -----------
 
@@ -779,6 +781,8 b' established.'
 
 This command does not accept any arguments. The return type is a ``string``.
 
+This command was introduced in Mercurial 0.9.1 (released July 2006).
+
 listkeys
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