[gcc r17-2725] doc: Fix up doc build

https://gcc.gnu.org/g:66a30b62d297b6cb3a5aefa56c53485b67b0bc63

commit r17-2725-g66a30b62d297b6cb3a5aefa56c53485b67b0bc63
Author: Jakub Jelinek <[email protected]>
Date:   Mon Jul 27 13:20:01 2026 +0200

    doc: Fix up doc build
    
    The last change in sourcebuild.texi uses @code(...) which makeinfo
    errors on:
    sourcebuild.texi:2122: @code expected braces
    sourcebuild.texi:2131: @code expected braces
    Fixed thusly.
    
    2026-07-27  Jakub Jelinek  <[email protected]>
    
            * doc/sourcebuild.texi (arm_neon_fp16_hw, arm_fp16_alternative_hw):
            Use @code{...} instead of @code(...).

Diff:
---
 gcc/doc/sourcebuild.texi | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/gcc/doc/sourcebuild.texi b/gcc/doc/sourcebuild.texi
index 31e0552a9249..2c41583ced51 100644
--- a/gcc/doc/sourcebuild.texi
+++ b/gcc/doc/sourcebuild.texi
@@ -2119,7 +2119,7 @@ options, including @code{-mfp16-format=ieee} if necessary to obtain the
 
 @item arm_neon_fp16_hw
 Test system supports executing Neon half-precision float instructions.
-(Implies @code(arm_neon_fp16_ok).)
+(Implies @code{arm_neon_fp16_ok}.)
 
 @item arm_fp16_alternative_ok
 ARM target supports the ARM FP16 alternative format.  Some multilibs
@@ -2128,7 +2128,7 @@ may be incompatible with the options needed.
 @item arm_fp16_alternative_hw
 Test system supports executing VFP half-precision floating-point
 instructions in the ARM FP16 alternative format.  (Implies
-@code(arm_fp16_alternative_ok).)
+@code{arm_fp16_alternative_ok}.)
 
 @item arm_fp16_none_ok
 ARM target supports specifying none as the ARM FP16 format.