qemu-check.exp: clean assertion failure message

The message displayed by "make check" when an assertion failure is
detected is as follows:

 $ PATH=~/work/clang-10.0.0/bin:$PATH make -j10 COMPILER=clang check
 [...]
 Starting QEMU... done, guest is booted.
 Running: xtest...
 '##########!!! TEE core assertion failed: 'assertion 'maps[map_idx].sz == sz' failed at ldelf/ta_elf.c:1351 in ta_elf_print_mappings()
 make: *** [Makefile:221: check] Error 1
 $

The "TEE core assertion failed:' part is not needed and possibly
misleading (in this case the assertion occurred in ldelf which is
arguably not "TEE core"). Remove it.

Signed-off-by: Jerome Forissier <jerome@forissier.org>
Acked-by: Jens Wiklander <jens.wiklander@linaro.org>
diff --git a/qemu-check.exp b/qemu-check.exp
index 645ee1b..e61d519 100644
--- a/qemu-check.exp
+++ b/qemu-check.exp
@@ -99,7 +99,7 @@
 	"+-----------------------------------------------------\r\r" {}
 	# Handle errors in TEE core output
 	-i $teecore -re {(assertion.*failed at.*)\n} {
-		info "!!! TEE core assertion failed: '$expect_out(1,string)'\n"
+		info "!!! $expect_out(1,string)\n"
 		exit 1
 	}
 	timeout {