Update incrcomp-debugging.md

[Tbkhi]

Minor formatting updates.

[Tbkhi]

Is TypeckTables still a part of the compiler?

https://doc.rust-lang.org/nightly/nightly-rustc/index.html?search=TypeckTables

src\queries\incremental-compilation-debugging.md
21:#[rustc_then_this_would_need(TypeckTables)] //~ ERROR OK
27:> If this (`foo`) is changed, then this (i.e. `bar`)'s `TypeckTables` would need to be changed.
35:#[rustc_then_this_would_need(TypeckTables)] //~ ERROR no path
40:> If `foo` is changed, then `baz`'s `TypeckTables` does not need to be changed.
78:RUST_DEP_GRAPH_FILTER='-> TypeckTables'
81:would select the predecessors of all `TypeckTables` nodes. Usually though you
82:want the `TypeckTables` node for some particular `fn`, so you might write:
85:RUST_DEP_GRAPH_FILTER='-> TypeckTables & bar'
88:This will select only the predecessors of `TypeckTables` nodes for functions
95:RUST_DEP_GRAPH_FILTER='Hir & foo -> TypeckTables & bar'
99:`TypeckTables(bar)`, from which you can (hopefully) see the source
125:Collect(bar) -> TypeckTables(bar)

[Tbkhi]

CC: @spastorino