MIPS/GAS: Remove extraneous `install_insn' call from `append_insn'

Complement:

commit 1e915849
Author: Richard Sandiford <rdsandiford@googlemail.com>
Date:   Wed Mar 9 09:17:02 2005 +0000

<https://sourceware.org/ml/binutils/2005-03/msg00217.html>, ("Rework
MIPS nop-insertion code, add -mfix-vr4130 [5/11]"), and remove a call to
`install_insn' from `append_insn', which as from that change has become
redundant.  This is because such a call, to place an instruction's bit
pattern in output, is already made from `move_insn', called from
`add_relaxed_insn' or `add_fixed_insn' as appropriate, either of which
now always is and has to be made from `append_insn' before the repeated
call to `install_insn' is made.  Previously the place where this second
invocation is made was the only one where the output stream was updated,
although the update was made inline rather than with a function call.

Remove the repeated call then, to reclaim some performance.

	gas/
	* config/tc-mips.c (append_insn): Remove extraneous
	`install_insn' call.