dApp API: remove redundnat "Sync dApp API" item under that TOC entry' "Aync dApp API" too

[hrischuk-da]

There is a redundant, second "Sync dApp API" item under the main "Sync dApp API" TOC entry. See the red box in the figure below.
It is not needed because there is a "Details and history" at the bottom of the entry.

NOTE: Many other entries have the same redundant removal need. Do this for:

• "Aync dApp API"
• "Wallet Gateway" --> "User API"
• "Wallet Gateway" --> "Signing API"

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