Bump BandedMatrix compat to v1

[codecov[bot]]

Codecov Report

All modified lines are covered by tests :white_check_mark:

Comparison is base (16cc267) 71.30% compared to head (7b6af5c) 70.47%. Report is 1 commits behind head on backport_0.8.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## backport_0.8 #607 +/- ## ================================================ - Coverage 71.30% 70.47% -0.83% ================================================ Files 81 81 Lines 8600 8604 +4 ================================================ - Hits 6132 6064 -68 - Misses 2468 2540 +72 ``` | [Files](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/607?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation) | Coverage Δ | | |---|---|---| | [src/Multivariate/TensorSpace.jl](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/607?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation#diff-c3JjL011bHRpdmFyaWF0ZS9UZW5zb3JTcGFjZS5qbA==) | `85.13% <100.00%> (+0.20%)` | :arrow_up: | ... and [19 files with indirect coverage changes](https://app.codecov.io/gh/JuliaApproximation/ApproxFunBase.jl/pull/607/indirect-changes?src=pr&el=tree-more&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=JuliaApproximation)

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