Remove MBEDTLS_ERR_SSL_CERTIFICATE_TOO_LARGE error code

This error is used when the output buffer isn't large enough
to hold our own certificate.

In the interest of cleaning up the error space for 3.0, this commit
removes MBEDTLS_ERR_SSL_CERTIFICATE_TOO_LARGE and replaces its single
use by MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL.

Signed-off-by: Hanno Becker <hanno.becker@arm.com>
diff --git a/include/mbedtls/error.h b/include/mbedtls/error.h
index 5916927..c219d67 100644
--- a/include/mbedtls/error.h
+++ b/include/mbedtls/error.h
@@ -107,8 +107,8 @@
  * SSL       5   2 (Started from 0x5F00)
  * CIPHER    6   8 (Started from 0x6080)
  * SSL       6   24 (Started from top, plus 0x6000)
- * SSL       7   30 (Started from 0x7080, gaps at
- *                   0x7300, 0x7800)
+ * SSL       7   29 (Started from 0x7080, gaps at
+ *                   0x7300, 0x7500, 0x7800)
  *
  * Module dependent error code (5 bits 0x.00.-0x.F8.)
  */