Fix T93353: Reload Library Override file loses Constraints, take II.

When adding `INSERT` operations over RNACollection items, rna diffing
code did not properly report the properties as not being equals.

This in turn triggered the 'purge unused exiting override properties'
mechanism, thus deleting the exitsting (valid) insert override property
operation.

NOTE: This should also be backported to 2.93, and probably 2.83.

Reviewed By: sybren, jbakker

Maniphest Tasks: T93353

Differential Revision: https://developer.blender.org/D13426

source/blender/makesrna/intern/rna_rna.c

@@ -1949,6 +1949,8 @@ int rna_property_override_diff_default(Main *bmain,
                    idx_a - 1);
 #  endif
             op = NULL;
+
+            equals = false;
           }
           else if (is_id || is_valid_for_diffing) {
             if (equals || do_create) {