Bump rexml from 3.3.4 to 3.3.6 #8543

Job	Run time
changes	3s
spm-binary-cron	0s
check	1m 42s
sanitizers-mac (macos-14, asan)	17m 23s
sanitizers-mac (macos-14, tsan)	17m 4s
cmake-prod-db (macos-14, (default))	15m 21s
cmake (macos-14)	15m 29s
cmake-prod-db (macos-14, test-db)	15m 25s
pod-lib-lint (FirebaseFirestoreInternal.podspec)	40m 44s
sanitizers-ubuntu (ubuntu-latest, asan)	20m 39s
pod-lib-lint (FirebaseFirestore.podspec)	34m 59s
cmake (ubuntu-latest)	18m 42s
spm-binary	5m 59s
spm-source (iOS, macos-13)	21m 8s
xcodebuild (iOS)	31m 25s
spm-source (iOS, macos-14)	18m 6s
xcodebuild (macOS)	38m 8s
spm-source (tvOS, macos-13)	21m 47s
xcodebuild (tvOS)	26m 32s
check-firestore-internal-public-headers	6s
spm-source (tvOS, macos-14)	17m 59s
spm-source (macOS, macos-13)	18m 31s
spm-source (macOS, macos-14)	13m 32s
pod-lib-lint-cron	0s
spm-source (macos-14, visionOS, Xcode_15.3)	19m 42s
Check all required Firestore tests results	1s
	7h 10m 27s

Provide feedback