Bump version to 2.28.5

```
./scripts/bump_version.sh --version 2.28.5
```

Signed-off-by: Minos Galanakis <minos.galanakis@arm.com>
diff --git a/doxygen/mbedtls.doxyfile b/doxygen/mbedtls.doxyfile
index adad131..f6f160d 100644
--- a/doxygen/mbedtls.doxyfile
+++ b/doxygen/mbedtls.doxyfile
@@ -1,4 +1,4 @@
-PROJECT_NAME           = "Mbed TLS v2.28.4"
+PROJECT_NAME           = "Mbed TLS v2.28.5"
 OUTPUT_DIRECTORY       = ../apidoc/
 FULL_PATH_NAMES        = NO
 OPTIMIZE_OUTPUT_FOR_C  = YES