Fix grammar in 2 strings in strings.xml

[jtbx]

Line 1580 of /vector/src/main/res/values/strings.xml reads

<string name="room_list_people_empty_body">Your direct message conversations will be displayed here. Tap the + bottom right to start some.</string>

Tap the + bottom right to start some is a grammar mistake, so I changed it to Tap the + at the bottom right to start some instead.

In line 1582 it says something similar, so I corrected that as well.

This error is also part of upstream Element code.

Edit: Upstream PR is element-hq#6132

[SpiritCroc]

Hi, thanks for creating this PR. Merging such upstream string changes into SchildiChat would not help for long though:
We don't change upstream strings manually to avoid merge conflicts. So if we want to have different strings then upstream, we automate this in correct_strings.sh. But for this one, it's better to just wait for upstream to merge the fix, then we'll get it with the next upstream merge.

[jtbx]

Okay, thanks. I'll leave the Element PR to be merged.