[FIX] web_editor: review two pairs of shape junctions

As the previous commit explained, there is sometimes a gap between two
shapes due to some browser rounding errors, especially when using
browser zoom. However, there are also some things we can do in our
shapes themselves to decrease this problem.

This commit fixes two pairs of shapes which were easily fixed by
reviewing the rounding of one path and making the viewBox a square
(making a viewBox a square is known to solve issues). However:
- The first pair is not entirely fixed, the error is just reduced.
- The second pair is fixed... but the shapes actually do not join very
  well (somehow the linear gradients do not seem to join properly)...
  but still better than a white line between the two.

Reminder: several commits had attempted to fix this before ([1], [2],
[3], [4]) (and this commit's parent). But that wasn't enough to stop it
happening. Some shapes still need to be fixed although that will likely
be done in future versions.

[1]: odoo@c0f6259
[2]: odoo@ac82407
[3]: odoo@42b3ad1
[4]: odoo@e386f31

task-2824607
opw-3069213
opw-3057533

closes odoo#108219

X-original-commit: 52e5afa
Signed-off-by: Quentin Smetz (qsm) <qsm@odoo.com>