Fix spurious semicolon in sparc-linux-nat.c

Remove a semicolon that should not be there, as reported in PR 23917:

  CXX    sparc-linux-nat.o
/home/emaisin/src/binutils-gdb/gdb/sparc-linux-nat.c:39:3: error: expected unqualified-id before ‘{’ token
   { sparc_store_inferior_registers (regcache, regnum); }
   ^

Tested by rebuilding the file manually (make sparc-linux-nat.o) in a
sparc64-linux-gnu build.

gdb/ChangeLog:

	PR gdb/23917
	* sparc-linux-nat.c (sparc_linux_nat_target): Remove extraneous
	semicolon.