doc: Remove latex math documentation

This hasn't worked since pandoc stopped being used. We can get by well enough
with the superscript extension for these equations.

Closes #12989

Author: alexcrichton

src/doc/rust.md

@@ -3269,12 +3269,12 @@ The primitive types are the following:
 The machine types are the following:
 
 * The unsigned word types `u8`, `u16`, `u32` and `u64`, with values drawn from
-  the integer intervals $[0, 2^8 - 1]$, $[0, 2^{16} - 1]$, $[0, 2^{32} - 1]$ and
-  $[0, 2^{64} - 1]$ respectively.
+  the integer intervals [0, 2^8 - 1], [0, 2^16 - 1], [0, 2^32 - 1] and
+  [0, 2^64 - 1] respectively.
 
 * The signed two's complement word types `i8`, `i16`, `i32` and `i64`, with
-  values drawn from the integer intervals $[-(2^7), 2^7 - 1]$,
-  $[-(2^{15}), 2^{15} - 1]$, $[-(2^{31}), 2^{31} - 1]$, $[-(2^{63}), 2^{63} - 1]$
+  values drawn from the integer intervals [-(2^(7)), 2^7 - 1],
+  [-(2^(15)), 2^15 - 1], $[-(2^(31)), 2^31 - 1], [-(2^(63)), 2^63 - 1]
   respectively.
 
 * The IEEE 754-2008 `binary32` and `binary64` floating-point types: `f32` and