Update pymavlink

[Williangalvani]

• [x] test
• [x] are submodules updated by the /git page?

Comparison:

Both tests had pingmav running, but no gcs connected:

0.0.26
    mavproxy.py at 68~80% cpu in htop

    Linux 4.9.24-v7+ (raspberrypi)  03/08/21    _armv7l_    (4 CPU)

    17:30:53        CPU     %user     %nice   %system   %iowait    %steal     %idle
    17:31:23        all     20.82      0.00      9.75      0.07      0.00     69.36
    17:31:53        all     21.80      0.00      8.58      0.07      0.00     69.55
    17:32:23        all     21.70      0.00      8.14      0.06      0.00     70.10
    17:32:53        all     18.35      0.00     11.69      0.08      0.00     69.87
    17:33:23        all     19.02      0.00     11.05      0.03      0.00     69.90
    17:33:53        all     21.98      0.00      8.00      0.03      0.00     69.99

0.0.27
    mavproxy at 45~55% cpu in htop

    pi@raspberrypi:~ $ sar 30
    Linux 4.9.24-v7+ (raspberrypi)  03/08/21    _armv7l_    (4 CPU)

    19:27:32        CPU     %user     %nice   %system   %iowait    %steal     %idle
    19:28:02        all     16.83      0.00      9.93      0.08      0.00     73.17
    19:28:32        all     19.33      0.00      6.38      0.09      0.00     74.20
    19:29:02        all     19.37      0.00      5.46      0.05      0.00     75.12
    19:29:32        all     18.97      0.00      7.39      0.05      0.00     73.59
    19:30:02        all     19.20      0.00      5.72      0.08      0.00     75.01
    19:30:32        all     19.68      0.00      5.81      0.01      0.00     74.50

There is a 0.0.27 tag in my remote for convenience.

To update:

1. open http://192.168.2.2:2770/git
2. add my remote https://github.com/williangalvani/companion.git
3. select my remmote (not sure if necessary)
4. click 'fetch'
5. under my remote, expand the tags section
6. click 0.0.27
7. click update
8. wait. this update my take a while, in the bad sd card i'm using, it took 19 min.