Revert back to tcell 2.2.0

tcell 2.2.1 has a bug [0][1][2] that made senpai need a keypress after
Ctrl-C was hit.

[0] gdamore/tcell#452
[1] gdamore/tcell#454
[2] gdamore/tcell@7694d90

go.mod

@@ -3,7 +3,7 @@ module git.sr.ht/~taiite/senpai
 go 1.14
 
 require (
-	github.com/gdamore/tcell/v2 v2.2.1
+	github.com/gdamore/tcell/v2 v2.2.0
 	github.com/mattn/go-runewidth v0.0.10
 	golang.org/x/term v0.0.0-20201210144234-2321bbc49cbf
 	gopkg.in/yaml.v2 v2.3.0

go.sum

@@ -1,7 +1,7 @@
 github.com/gdamore/encoding v1.0.0 h1:+7OoQ1Bc6eTm5niUzBa0Ctsh6JbMW6Ra+YNuAtDBdko=
 github.com/gdamore/encoding v1.0.0/go.mod h1:alR0ol34c49FCSBLjhosxzcPHQbf2trDkoo5dl+VrEg=
-github.com/gdamore/tcell/v2 v2.2.1 h1:Gt8wk0jd5pIK2CyXNo/fqwxNWf726j1lQjEDdfbnqTc=
-github.com/gdamore/tcell/v2 v2.2.1/go.mod h1:cTTuF84Dlj/RqmaCIV5p4w8uG1zWdk0SF6oBpwHp4fU=
+github.com/gdamore/tcell/v2 v2.2.0 h1:vSyEgKwraXPSOkvCk7IwOSyX+Pv3V2cV9CikJMXg4U4=
+github.com/gdamore/tcell/v2 v2.2.0/go.mod h1:cTTuF84Dlj/RqmaCIV5p4w8uG1zWdk0SF6oBpwHp4fU=
 github.com/lucasb-eyer/go-colorful v1.0.3 h1:QIbQXiugsb+q10B+MI+7DI1oQLdmnep86tWFlaaUAac=
 github.com/lucasb-eyer/go-colorful v1.0.3/go.mod h1:R4dSotOR9KMtayYi1e77YzuveK+i7ruzyGqttikkLy0=
 github.com/mattn/go-runewidth v0.0.10 h1:CoZ3S2P7pvtP45xOtBw+/mDL2z0RKI576gSkzRRpdGg=