[modclock] Redraw issues on time section

### Affected hardware version

Bangle 2

### Your firmware version

2v29

### The bug

### Description of Bug:
The previous time text remains when the text is redrawn, as a result remnants of previous time text exist when the time gets updated.

### Expected Behaviour:
The entire area that the text takes up should be cleared before the text gets drawn to remove remnants of past time text.

### Steps to Reproduce:
1. Install [modclock]
2. Wait for the time text to be less in length from the previous time text, and you will see remnants of previous text text usually on the edges

### Installed apps

widlock (0.08), wid_a_battery_widget (0.05), widbt_notify (0.18), widclk (0.08), widmsggrid (0.07), 2047pp (0.04), about (0.15), acmaze (0.05), agenda (0.20), alarm (0.52), altimeter (0.05), android (0.46), files (0.08), astroid (0.06), authentiwatch (0.07), hidmouse (0.01), clockbg (0.09), balltastic (0.04), barometer (0.04), boot (0.69), calculator (0.08), hidcam (0.04), cards (0.05), clock_info (0.27), compass (0.09), contacts (0.05), f9lander (0.05), flow (0.02), fileman (0.04), flappy (0.06), gpstime (0.05), gipy (0.28), grocery (0.06), health (0.37), hrm (0.13), henkinen (0.02), kineticscroll (0.05), messageicons (0.17), messages (0.70), messagegui (0.92), metronome (0.07), gbmusic (0.14), magnav (0.07), noteify (0.04), notify (0.14), openstmap (0.33), oxofocus (0.02), qcenter (0.07), quicklaunch (0.16), random (0.03), recorder (0.49), reply (0.03), runplus (0.31), sched (0.36), score (0.04), setting (0.82), smpltmr (0.13), sleeplog (0.25), snaky (0.01), sokoban (0.03), stacker (0.03), splitsw (0.01), trex (0.05), terminal (0.02), tetris (0.12), thermom (0.07), tinydraw (0.04), torch (0.11), kbtouch (0.05), waypointer (0.11), waypoints (0.10), weather (0.31), welcome (0.14), wid_edit (0.05), mylocation (0.11), iconlaunch (0.21), clkinfomsg (0.01), loadanim (0.02), twotwoclock (0.04)

Locate the modclock app in the BangleApps repository and reproduce the display issue by waiting for a shorter time value to be drawn. Inspect its time redraw path; done means the previous text is no longer visible around updated time values on Bangle 2 with firmware 2v29.

Written by the indexing model from the issue text.