tcl-testbench[x].sh: Use bash within shebang

These scripts using non Posix shell extensions which are provided by bash and
require the bash as shell to be fully functional.

examples/tclspice/tcl-testbench1/tcl-testbench1.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # -*- mode: tcl -*- \
         exec wish -f "$0" ${1+"$@"}
 

examples/tclspice/tcl-testbench3/tcl-testbench3.sh

@@ -1,4 +1,4 @@
-#!/bin/sh
+#!/bin/bash
 # -*- mode: tcl -*- \
         exec wish -f "$0" ${1+"$@"}