ld/doc: use "stack trace" instead of "unwind" for SFrame

SFrame format is meant for generating stack traces only.

ld/
	* ld.texi: Replace the use of "unwind" with "stack trace".

ld/ld.texi

diff --git a/ld/ld.texi b/ld/ld.texi
index db3a9f0..36005dc 100644
--- a/ld/ld.texi
+++ b/ld/ld.texi
@@ -2835,7 +2835,7 @@
 Request creation of @code{.eh_frame} unwind info for linker
 generated code sections like PLT.  This option is on by default
 if linker generated unwind info is supported.  This option also
-controls the generation of @code{.sframe} unwind info for linker
+controls the generation of @code{.sframe} stack trace info for linker
 generated code sections like PLT.
 
 @kindex --enable-new-dtags