Remove unused but conflicting \citet command

This thesis actually didn't use the '\citet' command, and what's worse,
this command has now been defined in package, so it's causing a conflict
and preventing from compilation.

thesis.tex

@@ -68,7 +68,6 @@
 \DeclareFieldFormat{pages}{#1\addperiod\space}
 %
 \newcommand{\citeay}[1]{\citeauthor{#1} \citeyear{#1} \parencite{#1}}
-\newcommand{\citet}[1]{\citeauthor{#1} (\citeyear{#1})\cite{#1}}
 
 % Change 'emph' style to bold face
 \let\emph\relax  % there's no \RedeclareTextFontCommand