Dockerfile: Update gstreamer to 1.26.2

Author: joaoantoniocardoso

Dockerfile

@@ -1,6 +1,6 @@
 # Global build environment variables
 ARG GST_INSTALL_DIR=/artifacts
-ARG GST_VERSION=1.24.8
+ARG GST_VERSION=1.26.2
 ARG LIBCAMERA_ENABLED=true
 ARG LIBCAMERA_VERSION=v0.3.1
 ARG RPICAM_ENABLED=false