Fix numeric separator Number transform

[jridgewell]

Q	A
Patch: Bug Fix?	Yes
Major: Breaking Change?	No
Minor: New Feature?	No
Deprecations?	No
Spec Compliancy?	Yes?
Tests Added/Pass?	Yes
Fixed Tickets
License	MIT
Doc PR
Dependency Changes

The transform assumed the argument to Number was always a string, which isn't correct. Now, we only remove the separators if it is in fact a string.

[codecov]

Codecov Report

Merging #5825 into 7.0 will decrease coverage by 0.06%.
The diff coverage is 100%.

@@            Coverage Diff             @@
##              7.0    #5825      +/-   ##
==========================================
- Coverage   84.95%   84.89%   -0.07%     
==========================================
  Files         284      284              
  Lines        9933     9934       +1     
  Branches     2781     2789       +8     
==========================================
- Hits         8439     8433       -6     
- Misses        982      991       +9     
+ Partials      512      510       -2

Impacted Files	Coverage Δ
...el-plugin-transform-numeric-separator/src/index.js	100% <100%> (ø)	⬆️
packages/babel-helper-fixtures/src/index.js	71.62% <0%> (-4.06%)	⬇️
packages/babel-helper-call-delegate/src/index.js	64% <0%> (-4%)	⬇️
packages/babel-traverse/src/path/context.js	85.34% <0%> (-1.73%)	⬇️
packages/babel-traverse/src/path/modification.js	72.11% <0%> (-0.97%)	⬇️
packages/babel-traverse/src/visitors.js	85.71% <0%> (-0.96%)	⬇️
packages/babel-types/src/definitions/es2015.js	96.15% <0%> (-0.52%)	⬇️
packages/babel-types/src/definitions/core.js	98.21% <0%> (-0.32%)	⬇️
...in-transform-es2015-template-literals/src/index.js	100% <0%> (ø)	⬆️
...bel-plugin-transform-es2015-classes/src/vanilla.js	90.63% <0%> (ø)	⬆️
... and 3 more

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[existentialism]

👍

[hzoo]

Nice work, super quick @jridgewell!

[hzoo]

Oh yeah, and cc @rwaldron (and please accept Babel org inv)