Fixed Desciption of unconditional_checked_cast_addr in SIL.rst

[freddi-kit]

What is it?

Fixing unconditional_checked_cast_addr description in SIL.rst

Why

Looks the description of unconditional_checked_cast_addr is a little wrong.
There is a %1 in the description of example code, but not shown on the example code of it (Looks SIL value of second oprand is wrong).

For Info

The bnf of unconditional_checked_cast_add is like below,

sil-instruction ::= 'unconditional_checked_cast_addr'
                     sil-type 'in' sil-operand 'to'
                     sil-type 'in' sil-operand

but example of it is following wrong format.

unconditional_checked_cast_addr $A in %0 : $@thick A to $B in $@thick B

The secound sil-operand is sil-type only but actual format of sil-operand is

sil-operand ::= sil-value ':' sil-type

[gottesmm]

LGTM

[gottesmm]

@swift-ci smoke test and merge