Remove centering for floats (#364)

This was a bad idea...:
https://tex.stackexchange.com/questions/2651/should-i-use-center-or-centering-for-figures-and-tables

floatrows not sure how it should work with flowcharts... so we use
centring

I don't want to redefine all floats either as we use them for chapters
title page.

book/sourdough-starter/sourdough-starter.tex

@@ -38,11 +38,10 @@ comes in handy. Let's look at the default recipe with baker's
 math and then adjust it for the \qty{1.4}{\kg} flour quantity.
 
 \begin{table}[!htb]
-\begin{center}
+\centering
   \input{tables/table-bakers-math-example.tex}
   \caption[Baker's math example]{An example table demonstrating how to
       properly calculate using baker's math}
-\end{center}
 \end{table}
 
 Note how each of the ingredients is calculated as a percentage
@@ -55,12 +54,11 @@ more flour available the next day. As mentioned the next day
 we have \qty{1.4}{\kg} at hand (\qty{1400}{\gram}).
 
 \begin{table}[!htb]
-    \begin{center}
+    \centering
         \input{tables/table-recipe-bakers-math.tex}
         \caption[Another baker's math example]{An example recipe that uses
             \qty{1400}{\gram} as its baseline and is then calculated using
             baker's math.}
-    \end{center}
 \end{table}
 
 For each ingredient we calculate the percentage
@@ -133,12 +131,11 @@ I~like to use a glass and place another
 inverted one on top.
 
 \begin{flowchart}[!htb]
-\begin{center}
+\centering
   \input{figures/fig-starter-process.tex}
   \caption[The full sourdough starter process]{The process of making a sourdough
       starter from scratch.}%
   \label{fig:sourdough-starter-process}
-\end{center}
 \end{flowchart}
 
 Now an epic battle begins. In one study~\cite{yeasts+biocontrol+agent}
@@ -272,14 +269,13 @@ yeast has been isolated like this from century old sourdough
 starters.
 
 \begin{flowchart}[!htb]
-\begin{center}
+\centering
   \input{figures/fig-starter-readiness.tex}
   \caption[Determining sourdough starter readiness]{A flow chart showing you how to
       determine if your sourdough starter is ready to be used.  For checking
       readiness look at a size increase and take note of your starter's smell.
       Both are important indicators to check for readiness.}%
   \label{fig:sourdough-starter-readiness}
-\end{center}
 \end{flowchart}
 
 The key sign to look at is bubbles that you see in your starter
@@ -346,7 +342,7 @@ yeast part of your sourdough and balance the fermentation.
 \section{Maintenance}
 
 \begin{flowchart}[!htb]
-\begin{center}
+\centering
   \input{figures/fig-starter-maintenance.tex}
   \caption[Sourdough starter maintenance flowchart]{A full flowchart showing
       you how to conduct proper sourdough starter maintenance. You can use a
@@ -356,7 +352,6 @@ yeast part of your sourdough and balance the fermentation.
       \qty{100}{\percent} hydration level. Adjust the water content
       accordingly when you use a stiff starter.}%
   \label{fig:sourdough-maintenance-process}
-\end{center}
 \end{flowchart}
 
 You have made your sourdough starter and your first bread. How do you perform