docs(info): rename functions in readme

README.md

@@ -11,9 +11,9 @@ Bot for the private server Discord "Les Copaings"
 ### XP
 
 Functions:
-- $xp_message(x;y) = \frac{0.025 x^{1.25}}{y^{-0.5}}+1$ where $x$ is the length of the message and $y$ is the diversity of the 
+- $xp-message(x;y) = \frac{0.025 x^{1.25}}{y^{-0.5}}+1$ where $x$ is the length of the message and $y$ is the diversity of the 
 message (number of different rune)
-- $xp_vocal(x)=0.01 x^{1.3}+1$ where $x$ is the time spent in vocal
+- $xp-vocal(x)=0.01 x^{1.3}+1$ where $x$ is the time spent in vocal
 - $level(x)=0.2 x^{0.5}$ where $x$ is the xp
 - $level^{-1}(x)=(5x)^2$ where $x$ is the level
 - $lose(x,y)= 10^{-2+\ln(x/85)}x^2+\lfloor y/100 \rfloor$ where $x$ is the inactivity time (hour) and $y$ is the xp