Bump rexml from 3.3.4 to 3.3.6 #5579

Job	Run time
quickstart (swift, macos-14, Xcode_15.3)	1m 19s
spm (iOS, macos-13)	8m 18s
spm (iOS, macos-14)	15m 42s
spm (tvOS, macos-13)	7m 51s
storage-integration-tests (Swift)	3m 29s
spm (tvOS, macos-14)	5m 56s
storage-integration-tests (ObjC)	3m 34s
spm (macOS, macos-13)	6m 21s
spm (macOS, macos-14)	5m 24s
spm (catalyst, macos-13)	7m 41s
spm (catalyst, macos-14)	7m 31s
spm (watchOS, macos-13)	7m 20s
spm (watchOS, macos-14)	7m 2s
spm (macos-14, visionOS, Xcode_15.3)	6m 10s
pod-lib-lint (ios, macos-14)	2m 51s
pod-lib-lint (ios, macos-13)	11m 35s
quickstart-ftl-cron-only	0s
pod-lib-lint (tvos, macos-14)	2m 56s
pod-lib-lint (tvos, macos-13)	8m 38s
pod-lib-lint (macos, macos-14)	2m 25s
pod-lib-lint (macos, macos-13)	5m 16s
pod-lib-lint (watchos, macos-14)	3m 6s
pod-lib-lint (watchos, macos-13)	3m 14s
storage-cron-only	0s
	2h 13m 39s

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