Newcomers.rst: Rename duplicate section
Newcomers.rst: Rename duplicate section

Two sections were named Start working, and one
is renamed to ``Picking up an issue``, to reflect
it correctly.

Fixes https://github.com/coala-analyzer/coala/issues/2324

Asnelchristian/coala,ayushin78/coala,arush0311/coala,yashtrivedi96/coala,abhiroyg/coala,ayushin78/coala,ManjiriBirajdar/coala,kartikeys98/coala,aptrishu/coala,impmihai/coala,karansingh1559/coala,arush0311/coala,CruiseDevice/coala,Balaji2198/coala,Asnelchristian/coala,Asnelchristian/coala,arush0311/coala,nemaniarjun/coala,karansingh1559/coala,jayvdb/coala,yashLadha/coala,incorrectusername/coala,meetmangukiya/coala,SanketDG/coala,aptrishu/coala,refeed/coala,Shade5/coala,mr-karan/coala,damngamerz/coala,meetmangukiya/coala,ManjiriBirajdar/coala,karansingh1559/coala,vinc456/coala,jayvdb/coala,Nosferatul/coala,coala/coala,nemaniarjun/coala,MariosPanag/coala,Asalle/coala,stevemontana1980/coala,kartikeys98/coala,sils1297/coala,abhiroyg/coala,yashLadha/coala,yashtrivedi96/coala,Balaji2198/coala,netman92/coala,vinc456/coala,Asalle/coala,yashtrivedi96/coala,JohnS-01/coala,Shade5/coala,CruiseDevice/coala,ayushin78/coala,NiklasMM/coala,mr-karan/coala,refeed/coala,damngamerz/coala,rimacone/testing2,JohnS-01/coala,netman92/coala,damngamerz/coala,sagark123/coala,coala-analyzer/coala,RJ722/coala,jayvdb/coala,refeed/coala,Shade5/coala,arjunsinghy96/coala,NiklasMM/coala,RJ722/coala,sils1297/coala,coala-analyzer/coala,JohnS-01/coala,ManjiriBirajdar/coala,shreyans800755/coala,incorrectusername/coala,vinc456/coala,SanketDG/coala,impmihai/coala,stevemontana1980/coala,sils1297/coala,coala/coala,tushar-rishav/coala,netman92/coala,kartikeys98/coala,coala/coala,SanketDG/coala,yashLadha/coala,MariosPanag/coala,shreyans800755/coala,nemaniarjun/coala,NiklasMM/coala,arjunsinghy96/coala,abhiroyg/coala,rimacone/testing2,stevemontana1980/coala,tushar-rishav/coala,Asalle/coala,MariosPanag/coala,Balaji2198/coala,sagark123/coala,shreyans800755/coala,mr-karan/coala,incorrectusername/coala,impmihai/coala,CruiseDevice/coala,Nosferatul/coala,tushar-rishav/coala,aptrishu/coala,sagark123/coala,RJ722/coala,arjunsinghy96/coala,meetmangukiya/coala,coala-analyzer/coala,Nosferatul/coala,rimacone/testing2