partially unindent R_{i,j} derivation

so that we're under GitLab's 1000 character limit for rendering maths

docs/megolm.md

@@ -40,30 +40,30 @@ advanced as follows:
 ```math
 \begin{aligned}
 R_{i,0} &=
-    \begin{cases}
-    H_0\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
-    R_{i-1,0} &\text{otherwise}
-    \end{cases}\\
+  \begin{cases}
+  H_0\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
+  R_{i-1,0} &\text{otherwise}
+  \end{cases}\\
 R_{i,1} &=
-    \begin{cases}
-    H_1\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
-    H_1\left(R_{2^{16}(m-1),1}\right) &\text{if }\exists m | i = 2^{16}m\\
-    R_{i-1,1} &\text{otherwise}
-    \end{cases}\\
+  \begin{cases}
+  H_1\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
+  H_1\left(R_{2^{16}(m-1),1}\right) &\text{if }\exists m | i = 2^{16}m\\
+  R_{i-1,1} &\text{otherwise}
+  \end{cases}\\
 R_{i,2} &=
-    \begin{cases}
-    H_2\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
-    H_2\left(R_{2^{16}(m-1),1}\right) &\text{if }\exists m | i = 2^{16}m\\
-    H_2\left(R_{2^8(p-1),2}\right) &\text{if }\exists p | i = 2^8p\\
-    R_{i-1,2} &\text{otherwise}
-    \end{cases}\\
+  \begin{cases}
+  H_2\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
+  H_2\left(R_{2^{16}(m-1),1}\right) &\text{if }\exists m | i = 2^{16}m\\
+  H_2\left(R_{2^8(p-1),2}\right) &\text{if }\exists p | i = 2^8p\\
+  R_{i-1,2} &\text{otherwise}
+  \end{cases}\\
 R_{i,3} &=
-    \begin{cases}
-    H_3\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
-    H_3\left(R_{2^{16}(m-1),1}\right) &\text{if }\exists m | i = 2^{16}m\\
-    H_3\left(R_{2^8(p-1),2}\right) &\text{if }\exists p | i = 2^8p\\
-    H_3\left(R_{i-1,3}\right) &\text{otherwise}
-    \end{cases}
+  \begin{cases}
+  H_3\left(R_{2^{24}(n-1),0}\right) &\text{if }\exists n | i = 2^{24}n\\
+  H_3\left(R_{2^{16}(m-1),1}\right) &\text{if }\exists m | i = 2^{16}m\\
+  H_3\left(R_{2^8(p-1),2}\right) &\text{if }\exists p | i = 2^8p\\
+  H_3\left(R_{i-1,3}\right) &\text{otherwise}
+  \end{cases}
 \end{aligned}
 ```