[Ecosystem > Explorers > Tonviewer] Fix wording

[verytactical]

Analyzing operations

The section should be called "reading a trace". We're not "analyzing" it.

The section should describe what the user sees, not how the user should follow arrows.

Instructions should be given for some use-case when user has to find something of importance. Finding the start of transaction chain (aka identify the entrpoint) is self-obvious: it starts at the only start.