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GH-41167: [CI][Release][GLib][Conda] Pin gobject-introspection to 1.78.1 (#41181)

### Rationale for this change

GObject Introspection is merging into GLib. It's not completed yet.

GLib related `.gir` files are moved to GLib from GObject Introspection since GLib/GObject Introspection 2.80.0. But glib 2.80.0 conda package doesn't support this merge yet:  https://github.com/conda-forge/glib-feedstock/pull/174

### What changes are included in this PR?

Pin gobject-introspection to 1.78.1 for now. 

### Are these changes tested?

Yes.

### Are there any user-facing changes?

No.
* GitHub Issue: #41167

Authored-by: Sutou Kouhei <kou@clear-code.com>
Signed-off-by: Sutou Kouhei <kou@clear-code.com>