perldelta: Remove error/warning explanations

Only the text of these should be present in a delta, with a link to the
full explanation.  Most of perldelta conformed to this, but not all.

pod/perldelta.pod

@@ -1036,11 +1036,6 @@ diagnostic messages, see L<perldiag>.
 
 L<%s must not be a named sequence in transliteration operator|perldiag/"%s must not be a named sequence in transliteration operator">
 
-(F) Transliteration (C<tr///> and C<y///>) transliterates individual
-characters.  But a named sequence by definition is more than an
-individual character, and hence doing this operation on it doesn't make
-sense.
-
 =item *
 
 L<Can't find Unicode property definition "%s" in regex;|perldiag/"Can't find Unicode property definition "%s" in regex; marked by <-- HERE in m/%s/">
@@ -1049,9 +1044,6 @@ L<Can't find Unicode property definition "%s" in regex;|perldiag/"Can't find Uni
 
 L<Can't redeclare "%s" in "%s"|perldiag/"Can't redeclare "%s" in "%s"">
 
-(F) A "my", "our" or "state" declaration was found within another declaration,
-such as C<my ($x, my($y), $z)> or C<our (my $x)>.
-
 =item *
 
 L<Character following \p must be '{' or a single-character Unicode property name in regex;|perldiag/"Character following \%c must be '{' or a single-character Unicode property name in regex; marked by <-- HERE in m/%s/">
@@ -1069,9 +1061,6 @@ L<Illegal user-defined property name|perldiag/"Illegal user-defined property nam
 
 L<Invalid number '%s' for -C option.|perldiag/"Invalid number '%s' for -C option.">
 
-(F) You supplied a number to the -C option that either has extra leading
-zeroes or overflows perl's unsigned integer representation.
-
 =item *
 
 L<<< Sequence (?... not terminated in regex; marked by S<<-- HERE> in mE<sol>%sE<sol>|perldiag/"Sequence (?... not terminated in regex; marked by <-- HERE in mE<sol>%sE<sol>" >>>
@@ -1101,25 +1090,6 @@ perldiag/Assuming NOT a POSIX class since %s in regex; marked by <-- HERE in mE<
 
 L<%s() is deprecated on :utf8 handles|perldiag/"%s() is deprecated on :utf8 handles">
 
-(W deprecated) The sysread(), recv(), syswrite() and send() operators
-are deprecated on handles that have the C<:utf8> layer, either
-explicitly, or implicitly, eg., with the C<:encoding(UTF-16LE)> layer.
-
-Both sysread() and recv() currently use only the C<:utf8> flag for the
-stream, ignoring the actual layers.  Since sysread() and recv() do no
-UTF-8 validation they can end up creating invalidly encoded scalars.
-
-Similarly, syswrite() and send() use only the C<:utf8> flag, otherwise
-ignoring any layers.  If the flag is set, both write the value UTF-8
-encoded, even if the layer is some different encoding, such as the
-example above.
-
-Ideally, all of these operators would completely ignore the C<:utf8>
-state, working only with bytes, but this would result in silently
-breaking existing code.  To avoid this a future version of perl will
-throw an exception when any of sysread(), recv(), syswrite() or send()
-are called on handle with the C<:utf8> layer.
-
 =back
 
 =head2 Changes to Existing Diagnostics