region: Fix input source options not being applied.

This was broken in a86cf1ec (3.32) when the input options dialog was converted
into a GtkPopover. Previously two GSettings objects were used, with one set to
'delay-apply' mode. The input source option didn't apply the changes.

The 'delay-apply' mode is from the original commit d3852fc8, however code was
simplified in b3199dd6 to only set one setting. This meant that the delay is no
longer necessary.

Fixes #440
11 jobs for <span class="ref-name">region-input-settings-no-delay</span> in 4 minutes and 39 seconds (queued for 2 seconds)
Status Job ID Name Coverage
  Build
passed #267315
build

00:01:48

 
  Test
passed #267317
asan

00:02:49

passed #267316
test

00:02:38

 
  Manual
manual #267322
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armv8
manual #267318
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flatpak
manual #267321
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msan
manual #267323
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ppc64le
manual #267319
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tsan
manual #267320
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  Review
manual #267324
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review
manual #267325
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