Update pubspec.yaml to lower SDK constraints and upgrade dependencies

[abhishekkhinde04]

Description

Replace this paragraph with a description of what this PR is changing or adding, and why. Consider including before/after screenshots.

List which issues are fixed by this PR. You must list at least one issue.

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Additional context

Pre-launch Checklist

• The Documentation is updated accordingly, or this PR doesn't require it.
• The ExampleAppChangelog is updated with related tickets, or this PR doesn't require it.
• I updated/added relevant documentation (doc comments with ///).
• I listed at least one issue that this PR fixes in the description above.
• I read and followed the Flutter Style Guide, including Features we expect every widget to implement.
• I added new tests to check the change I am making, or this PR is test-exempt.
• All existing and new tests are passing.