docs: Fix typo
Remove the quote before parens
@@ -1614,7 +1614,7 @@ during tests. It should be passed as the `env` keyword argument to
tests. It has the following methods.
- `append(varname, value)` appends the given value to the old value of
- the environment variable, e.g. `env.append'('FOO', 'BAR', separator
+ the environment variable, e.g. `env.append('FOO', 'BAR', separator
: ';')` produces `BOB;BAR` if `FOO` had the value `BOB` and plain
`BAR` if the value was not defined. If the separator is not
specified explicitly, the default path separator for the host
