gst-inspect: fix --exists for plugins with versions other than GStreamer's version, like the Rust plugins

The gst_plugin_feature_check_version is incorrect here as it is being used to compare the plugin's own version against the gstreamer library version, which are not related.

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The main issue at hand is when checking if an element exists via gst-inspect-1.0 --exists <element> will return non-zero if the plugin's version does not fit within the major/minor versions of the GStreamer library itself. You can view this behavior in the log by setting GST_DEBUG=*:DEBUG and running the command. The log will end with something like the following (in this example, against 1.22.9) before returning 1:

Checking whether 0.2.1 >= 1.22.0? no

Conversely, running gst-inspect-1.0 <element> succeeds and prints the element's information (and a zero exit value).