Resolve TextTheme deprecated members in various dart files #5

[ishitakapoor26]

• Resolve TextTheme deprecated members in various dart files.
• Replaced 'bodyText1' with bodyLarge.
• Replaced 'headline6' with titleLarge.
• Replaced 'subtitle1' with titleMedium.
• Replaced 'caption' with bodySmall.
• Removed typo in a file.
• Resolves #5

[CLAassistant]

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