Change spaces to a tab in a makefile recipe

Signed-off-by: Andrzej Kurek <andrzej.kurek@arm.com>
diff --git a/tests/data_files/Makefile b/tests/data_files/Makefile
index 7b0229f..2ad5c2a 100644
--- a/tests/data_files/Makefile
+++ b/tests/data_files/Makefile
@@ -476,7 +476,7 @@
 	hexdump -ve '1/1 "%.2X"' $< | sed "s/0355040A0C0A4D414C464F524D5F4D45/1555040A0C0A4D414C464F524D5F4D45/" | xxd -r -p > $@
 
 parse_input/rsa_single_san_uri.crt.der rsa_single_san_uri.crt.der: rsa_single_san_uri.key
-  $(OPENSSL) req -x509 -outform der -nodes -days 7300 -newkey rsa:2048 -key $< -out $@ -addext "subjectAltName = URI:urn:example.com:5ff40f78-9210-494f-8206-c2c082f0609c" -extensions 'v3_req' -subj "/C=UK/O=Mbed TLS/CN=Mbed TLS URI SAN"
+	$(OPENSSL) req -x509 -outform der -nodes -days 7300 -newkey rsa:2048 -key $< -out $@ -addext "subjectAltName = URI:urn:example.com:5ff40f78-9210-494f-8206-c2c082f0609c" -extensions 'v3_req' -subj "/C=UK/O=Mbed TLS/CN=Mbed TLS URI SAN"
 
 parse_input/rsa_multiple_san_uri.crt.der: rsa_multiple_san_uri.key
 	$(OPENSSL) req -x509 -outform der -nodes -days 7300 -newkey rsa:2048 -key $< -out $@ -addext "subjectAltName = URI:urn:example.com:5ff40f78-9210-494f-8206-c2c082f0609c, URI:urn:example.com:5ff40f78-9210-494f-8206-abcde1234567" -extensions 'v3_req' -subj "/C=UK/O=Mbed TLS/CN=Mbed TLS URI SAN"