Typo fix: cargo cov -> cargo profdata

src/doc/unstable-book/src/compiler-flags/source-based-code-coverage.md

@@ -128,7 +128,7 @@ $ cargo profdata -- --help  # note the additional "--" preceding the tool-specif
 
 ## Creating coverage reports
 
-Raw profiles have to be indexed before they can be used to generate coverage reports. This is done using [`llvm-profdata merge`] (or `cargo cov -- merge`), which can combine multiple raw profiles and index them at the same time:
+Raw profiles have to be indexed before they can be used to generate coverage reports. This is done using [`llvm-profdata merge`] (or `cargo profdata -- merge`), which can combine multiple raw profiles and index them at the same time:
 
 ```shell
 $ llvm-profdata merge -sparse formatjson5.profraw -o formatjson5.profdata